Javascript string indexof This method returns -1 if the value to search for never occurs. Feb 5, 2025 · A comprehensive guide to the JavaScript Array indexOf() method, covering its syntax, usage, and practical examples for finding the index of elements within an array. indexOf () method in JavaScript is used with strings to find the position of the first occurrence of a specified value. indexOf ()方法是用來搜索， 並傳回指定子字串在字串中第一次出現的位置 ( 由左至右 )，位置是由0開始計算。 除了可以從字串頭開始尋找外，也可以指定開始搜索的起始位置。 如果找不到指定字串會傳回-1。 要注意一點！String. Nov 2, 2023 · The indexOf() method and the includes() method in JavaScript are both used for searching within a string to check for the existence of… How can I find the index within an array of objects meeting some condition? For example, given this input: String. It returns the position of the substring, or -1 if the substring is not present. 4567', this can be accomplished with Feb 4, 2023 · Discover the powerful use of JavaScript indexOf() method to search for a substring & retrieve its index from a string and array. It also accepts a zero-based integer value to start its search from, e. If the substring is not found, it returns -1. The JavaScript string indexOf () method retrieves the position of a char value present in the given string. var noPic = largeSrc. In this tutorial, we will learn how to use indexOf method with examples. indexOf('bar') !== -1 is better comparable to /bar/. ' within the string '123. indexOf ("hi") returns -1. Jul 10, 2025 · The indexOf() method of Array instances returns the first index at which a given element can be found in the array, or -1 if it is not present. String. For example, "hello". It returns the index of where the string is first found, from the beginning of the search string. It takes an optional starting position and returns the last occurrence of the specified substring at an index less than or equal to the specified number. Tip: Use the lastIndexOf method to return the position of the last occurrence of specified character (s) in a string. indexOf returns the index of the a search term within a string. It returns the index position of the substring if found, or -1 if the substring is not present, which makes it useful for various string manipulation tasks. Jan 1, 2022 · The indexOf function of a string does not return a character but rather returns the position of the first place that string or character is found, not the character itself. The lastIndexOf() method returns -1 if the value is not found. The W3Schools online code editor allows you to edit code and view the result in your browser Aug 22, 2023 · The string. g. If the specified substring is not found, it returns -1. The lastIndexOf() method returns the index from the beginning (position 0). May 8, 2020 · The JavaScript indexOf method allows programmers to find out whether a string or array contains a value, and returns the index number at which that value starts. toLowerCase(). Jul 10, 2025 · Description Strings are useful for holding data that can be represented in text form. The JavaScript String indexOf () method is used to find the index of the first occurrence of the specified substring in the original string. Javascript indexOf() method is one of the most useful method of Javascript string. indexOf() 将返回 substring 的第一个字符在 string 中的位置。 Aug 22, 2020 · 查找字串時，有三種較常見的方法，分別為 search、indexOf、includes，都能夠辨別出字串裡是否有想要查找的文字。今天就來簡單認識一下這三種方法 The indexOf() function for strings returns the index of the first occurrence of the specified substring. indexOf() method, like this: pos = string. The indexOf() method returns the first index (position) of a specified value. Jul 8, 2025 · Learn how to use indexOf() in JavaScript with syntax, examples, best practices, and comparisons with includes(). If the string is not found, indexOf returns -1. Jun 23, 2021 · Syntax string. Feb 25, 2025 · The Indexof in JavaScript is used to return the starting position of the word. You seem to be doing a search and then converting the case, so that isn't going to help you. The JavaScript string indexOf method is a powerful and efficient way to search inside strings and is commonly used in text processing, filtering, and validation. 定义和用法 indexOf () 方法可返回某个指定的字符串值在字符串中首次出现的位置。 如果没有找到匹配的字符串则返回 -1。 注意： indexOf () 方法区分大小写。 提示： 同样你可以查看类似方法 lastIndexOf () 。 Description The indexOf() method returns the position of the first occurrence of a value in a string. You can normalize the case between the Array and the search term. indexOf (searchValue [, fromIndex]) Parameters … Aug 29, 2022 · JavaScript String indexOf () Summary: in this tutorial, you’ll learn how to use the JavaScript String indexOf() method to find the index of a substring within a string. search () – locate a substring in a string using a regular expression. indexOf(searchValue[, fromIndex]) Returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex, returns -1 if the value is not found. In this tutorial, we will learn about the JavaScript String indexOf () method with the help of examples. The method returns a 0-based index, making it a fundamental JavaScript string manipulation way. example: 说明 String. Dec 20, 2017 · 1 indexOf returns a -1 if the search is not in the string. Feb 6, 2020 · JavaScript String indexOf () indexOf () 方法用來判斷字串 字串 變數中是否包含某字串。 語法： str. indexOf () that takes a regular expression instead of a string for the first first parameter while still allowing a second parameter ?,and I am testing as follow to make sure that at least for one character regexp, the result is the same as if we used indexOf,To start the search from a particular position (faking the Apr 10, 2017 · プログラミング初心者向けに、JavaScriptで【indexOf】を使う方法を解説した記事です。本記事では、indexOfをどんな時に使うのか、書き方の例などを紹介します。実際のサンプルを書きながら解説しているので、参考にしてみてください。 The indexOf () method returns the position of the first occurrence of a specified value in a string. Jul 10, 2025 · The indexOf() method of String values searches this string and returns the index of the first occurrence of the specified substring. The indexOf() method starts at a specified index and searches from left to right (from the given start postion to the end of the array). Dec 19, 2022 · The indexOf method is a widely used tool in JavaScript for finding the position of a specified value within an array or a string. It offers a user-friendly but limited functionality, similar to JavaScript's pattern-matching regular expressions (the RegExp object, covered in later tutorials). JavaScript String indexOf () The indexOf() method returns the index (position) of the first occurrence of a string in a string, or it returns -1 if the string is not found: Nov 13, 2024 · The indexOf() function in JavaScript is a versatile tool for identifying the position of characters or substratches within strings. In JavaScript, indexOf () is a string method that is used to find the location of a substring in a string. This tutorial explains the indexOf () method, part of the JavaScript String object. Additionally, you can specify an index, defined by num in the syntax definition, to start your search for the string specified. Jun 6, 2023 · JavaScript is an essential language for web development, and understanding its core features and methods is crucial for every developer. I have string as this is test for alternative. The indexOf () method of an instance of the String object returns the indexed start position of the string passed. Using JavaScript toLowerCase () Method Transform the search string and elements of the array to the lowercase using the . indexOf () method The indexOf () method of the String class in JavaScript returns the index within the calling String object of the first occurrence of the specified value, searchString, starting the search at fromIndex. Dec 17, 2019 · An overview of how the indexOf() method works to find the position of a substring in a string or an item in an array in Javascript. If the string that is passed as a parameter to the indexOf()… Sep 8, 2017 · indexOf JavaScript method explained: learn how to easily use indexOf JavaScript method in your projects. If the string is not present, it returns -1. JavaScript indexOf method return index position of the first occurrence of a given string. In javascript, is there an equivalent of String. Apr 4, 2025 · JavaScript indexOf tutorial shows how to find elements in JavaScript arrays and strings. How can I do this in JavaScrip The W3Schools online code editor allows you to edit code and view the result in your browser Aug 28, 2019 · Curious about JavaScript indexOf vs includes performance on a string ? Let's dive in and see if one method is faster than the other. lastIndexOf () – find the The indexOf method takes a string and returns the index within the receiver at which the first instance of that string begins. The String. These sections introduce the string search methods that allow you to locate and verify substrings within strings. This method can be used to find out if a sub-string is included in a string or not. The indexOf () method returns the first index at which a specified string can be found in the given String object. In this tutorial, we will learn about the JavasScript String lastindexof () method with the help of examples. indexOf(searchValue[, fromIndex]) searchValue 是你要搜尋的字串 fromIndex 從哪個位置開始找起，預設為 0 返回找到的位置，第一個位置從 0 開始算起；找不到則返回 -1 用法： The indexOf () method returns the position of the first occurrence of a specified value in a string. It is case-sensitive. The indexOf() method is case sensitive. str. prototype. The tutorial provides numerous examples to demonstrate element searching in JS. The indexOf () method allows you to retrieve the position index of the first instance of a substring in a given string. The indexOf() method of String values searches this string and returns the index of the first occurrence of the specified substring. So in order to check if your variable starts with "1|Accept" you should check if indexOf returns 0. One such method is indexOf (), which is used to locate a substring within another string and Jan 14, 2025 · The indexOf () method in JavaScript is a useful tool for locating the index of the first occurrence of a specified value within a string. indexOf() that takes a regular expression instead of a string for the first parameter, while still allowing a second parameter ? I need to do some This JavaScript tutorial explains how to use the string method called indexOf () with syntax and examples. In this tutorial, you'll learn how to use the JavaScript String indexOf() method to find the index of a substring within a string. The indexOf() method returns -1 if the value is not found. Definition and Usage The indexOf() method returns the position of the first occurrence of specified character (s) in a string. indexOf() 方法从头到尾检索字符串 string，看它是否包含子串 substring。 开始检索的位置在字符串 string 的 start 处或 string 的开头（没有指定 start 参数时）。 如果找到了一个 substring，那么 String. Jul 13, 2017 · The indexOf () method returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex. toLowerCase () method, then perform the simple search. Dec 12, 2024 · JavaScript provides several methods to work with strings efficiently, enabling you to implement search features in your applications seamlessly. Dec 21, 2011 · I am learning Javascript and don't understand why the indexOf below returns -1: var string = "The quick brown fox jumps over the lazy dog"; console. Sep 28, 2024 · The IndexOf method is a built-in function in JavaScript that returns the position of the first occurrence of a specified substring within a string. By returning a numeric index or -1 when not found, it provides a robust way to handle string search operations efficiently. while arr. Description The indexOf() method returns the position of the first occurrence of a value in a string. indexOf(" In this tutorial of our JavaScript course for Beginners, we are going to learn about JavaScript String IndexOf and javascript string the last index of. indexOf() case insensitive. test('foo') because both result in a bool value. I am trying to find if an image has in its source name noPic which can be in upper or lower case. Sep 30, 2024 · The indexOf () method in JavaScript is used to find the index of the first occurrence of a specified value within a string. For example, if I had "scissors" in variable and wanted to know the position of all occurrences of the letter "s", it should print out 1, 4, 5, 8. I have created a indexof function in but it is not giving the correct output: Question is: /* Implement a function called indexOf that accepts two parameters: a string and a Aug 31, 2024 · The JavaScript String indexOf () method is a powerful tool that allows you to search for the first occurrence of a specified substring within a given string. indexOf('searchedElement') !== -1 to know if something exists in a string or an array is less more readable. Performances Oct 2, 2012 · In the first alert (), JavaScript returned "-1" - in other words, indexOf () did not find a match: this is simply because "JavaScript" is in lowercase in the first string, and properly capitalized in the second. It works similarly to indexOf() but searches from the end of the string. Feb 5, 2025 · A comprehensive guide to the JavaScript String indexOf() method, explaining how to find the index of a substring within a string. It provides a robust foundation for building modern applications and is widely used across the industry. I know I could have done this using alert (myString. Searching Mastering the string search methods can help you analyze text more efficiently. indexOf is more comparable to String. Syntax str. May 21, 2012 · From MDN: string. Examples Find the index of string: The indexOf() method returns the index within the calling String object of the first occurrence of the specified value, starting the search at fromIndex. For example > -1 is another way of saying !== -1 though I personaly prefer the latter. That said, for simple expressions without groups and anchors the performance should be comparable. startSearch (optional), indicates the index to start the search at. By default the search starts at the first element and ends at the last. indexOf() returns the index of the first occurrence of substring (substr) in a string (str): Jan 30, 2013 · 在jjavascript中，String. Jun 16, 2019 · IndexOf () - it accepts string literals or string objects but not regular expressions. The lastIndexOf() method is case sensitive. indexOf ("lo") returns 3, while "hello". What I want to find is location of for. This method is 0-based and case-sensitive, meaning the case of the characters must match exactly for a match to occur. indexOf () – get the index of the first occurrence of a substring in a string. indexOf() supports second param, fromIndex (doc). For example, given the string: I learned to play the Ukulele in Lebanon. indexOf("nopic"); Should I write : var noPic = largeSrc. : Actually String. these Learn how to use the indexOf function in JavaScript to find the index of a string or substring within a string. This method returns the position of the first instance of a certain value within that string. indexOf是會區分大小寫的。 I'm trying to find the positions of all occurrences of a string in another string, case-insensitive. If it does not find a substring, it returns -1; otherwise, it returns the starting index. includes('searchedElement') does what it says and it is obvious that it returns a boolean. JavaScript string indexOf examples included. Full guide with code examples. Jun 21, 2025 · Learn how to find substrings using JavaScript methods like indexOf, search, match, and includes. This is because indexOf will return the position of the search term in the string. Section 1. indexOf () is a fundamental concept in javascript development that every developer should understand. In this blog post, we'll dive deep into the indexOf() string method in JavaScript, its usage, and some practical examples to better understand its implementation Aug 29, 2020 · The indexOf() method is useful for determining the index at which a string starts at, if that string is contained inside another string. Perfect for beginners. One such method is the indexOf() method, which can be highly useful when working with strings. lastIndexOf () method, but it starts at the beginning of the string. I am new to JavaScript. Sep 19, 2013 · Javascript's String. indexOf(value, startSearch); value is the value to search for in a string. I would like to get the starting position of the 2nd occurrence of ABC with something like this: var string = "XYZ 123 ABC 456 ABC 789 ABC"; getPosition (string, 'ABC', 2) // --> 16 How would yo Jul 12, 2025 · Here are the different methods to make Array. In this article, you will learn about the indexOf () method of String with the help of examples. The JavaScript indexOf () method allows you to find out if a string contains one or more characters, and if so, the starting position of that set of characters If you’ve ever found yourself saying: “How do I figure out if one string contains a certain character or a sub-string?” then the JavaScript indexOf () method is for you. indexOf("good")); Jul 23, 2025 · Using String lastIndexOf () Method The lastIndexOf() method finds the index of the last occurrence of a specific character in a string. Jul 13, 2014 · You can't make . indexOf () case insensitive in JavaScript 1. Any I'm trying to get a case-insensitive search with two strings in JavaScript working. Some of the most-used operations on strings are to check their length, to build and concatenate them using the + and += string operators, checking for the existence or location of substrings with the indexOf() method, or extracting substrings with the substring() method. 35 Basically indexOf() is a method belongs to string (array object also), But while calling the function you are passing a number, try to cast it to a string and pass it. If it is not found, JavaScript indexof return -1. The lastIndexOf() method searches the string from the end to the beginning. Description The lastIndexOf() method returns the index (position) of the last occurrence of a specified value in a string. The boolean expression 'foo'. Returns -1 if the value is not found. Creating strings Strings can be The indexOf() method of String values searches this string and returns the index of the first occurrence of the specified substring. indexOf(c); For example, if you want to find the position of the character '1' or '. Sep 9, 2019 · Learn how to use String. Question: How do I locate the position of a given character in a string variable? Answer: To determine the position of a given character c (or a given substring c) within a string, use the JavaScript string. search because both will return the start index of the match. log (string. indexOf() は String 値のメソッドで、この文字列を検索し、指定した部分文字列が最初に出現するインデックスを返します。 オプションで開始位置を取り、指定した数値以上のインデックスで指定した部分文字列が最初に出現するインデックスを返します。 Learn how to use the JavaScript indexof() method for returning array and string index values, character or word positions, etc. It basically returns the index of the particular element in the array. Well organized and easy to understand Web building tutorials with lots of examples of how to use HTML, CSS, JavaScript, SQL, Python, PHP, Bootstrap, Java, XML and more. Learn about how to use the indexOf method on Career Karma. In this tutorial, you'll learn how to use the JavaScript String lastIndexOf() method to locate the last occurrence of a substring in a string. The indexOf () method is case-sensitive and zero-indexed. toUpperCase() on the dnameVal before the search, but that would only work if all the names are also upper case. In this article, you will learn about the lastIndexOf () method of String with the help of examples. indexOf ("for")), however I don't want to use indexOf. and the search strin. If you store the result of the first indexOf, just reuse it. Nov 9, 2025 · String. You could do . This method is the same as the String. It takes an optional starting position and returns the first occurrence of the specified substring at an index greater than or equal to the specified number. match is wasting doing too Oct 1, 2025 · The lastIndexOf() method of String values searches this string and returns the index of the last occurrence of the specified substring. Sep 30, 2025 · JavaScript String indexOf () is a built-in method that searches for the first occurrence of a specified substring within a string and returns its starting index. Normally it would be like this: var string="Stackoverflow is the BEST"; var result= string. search(/best/i); alert( Sep 10, 2024 · Answer by Cody Castaneda In javascript, is there an equivalent of String. While searching a string, includes accepts regexpes as opposed to indexOf Readability arr. Jan 30, 2023 · The indexOf() method is a built-in JavaScript method that returns the first incidence of the string in the string calling the method. indexOf() method to check if a string contains a substring in JavaScript. The W3Schools online code editor allows you to edit code and view the result in your browser The indexOf() method of String values searches this string and returns the index of the first occurrence of the specified substring. Jul 7, 2025 · Learn how to use indexOf() in JavaScript with syntax, examples, use cases, and best practices for arrays and strings. zgi kaun pogyodu tqtsbvm zetsuz vwrxm ocxagi gkztbb doems mlnl lqcqpvte szqssm tmozp mwbn ixiwgnm