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JavaScript String Contains: How to check a string exists in another

In this tutorial, you’ll learn how to use the JavaScript String Contains function to determine whether a string exists in another.

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In a bit of a spoiler, there actually is no contains function in JavaScript but if you want to use JavaScript to check if a string contains a substring.

There are a few ways you can check if a certain substring exists in a string with JavaScript but we’ll focus on a classic, pre-ES6 way, using the indexOf function which will give you the most browser compatibility.

Using the indexOf function you check where a JavaScript string contains characters that you pass as an argument. If the string exists, you get a positive value indicating the position of the substring in the base string. If the string doesn’t exist, you receive a value of -1.

By checking the returned value of indexOf you can determine whether the string contains the substring.

This traditional method will appear in a lot of legacy code but we’ll also take a quick look at the ES6 version of this technique which is using the string includes function which operates in a similar way as indexOf but returns a boolean value.

Other videos in the JavaScript Snippets series:
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How to find the longest word in a String with JavaScript:
How to reverse a String in JavaScript Tutorial:
Javascript String Length: How to determine the size of a string:
JavaScript join method: How to merge arrays into one value:
JavaScript How To Remove An Item From Array Tutorial:
Javascript How To Convert String To Number Tutorial:
JavaScript Create HTML Element: How to dynamically add tags to your pages:
JavaScript String Contains: How to check a string exists in another:
Link JavaScript to HTML: How to run your JavaScript code in the browser:
JavaScript Copy Array: How to make an exact copy of an array in JavaScript:
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Javascript Print To Console Tutorial: Different ways to output data to the console:


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