Replace a String case insensitive in JavaScript

Replace a String case insensitive in JavaScript - String.replace #

To do a case insensitive string replacement in JavaScript:

1. Call the String.replace method
2. Set the ignore flag on the first parameter

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// Supported in IE 6-11

const str = 'HELLO HELLO world';
const replaced = str.replace(/hello/gi, 'bye');
console.log(replaced); // 👉️ bye bye world

In the code snippet, we've used the String.replace method to replace all occurrences of the string hello with the string bye.

Note that we've set the i and g flags on the regular expression.

The i flag stands for ignore and does a case insensitive search in string.

The g flag stands for global and replaces all occurrences of the matched string.

If you only want to do a case insensitive replacement the first time the regular expression matches the string, remove the g flag:

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const str = 'HELLO HELLO world';

const replacedOnce = str.replace(/hello/i, 'bye');
console.log(replacedOnce); // 👉️ bye HELLO world

In the code example the regular expression is matched in the string two times, however we haven't set the g flag so only the first match is replaced.