Case insensitive regex in JavaScript

Question

I want to extract a query string from my URL using JavaScript, and I want to do a case insensitive comparison for the query string name. Here is what I am doing:

var results = new RegExp('[\\?&]' + name + '=([^&#]*)').exec(window.location.href);
if (!results) { return 0; }
return results[1] || 0;

But the above code does a case sensitive search. I tried /<regex>/i but it did not help. Any idea how can that be achieved?

Answer 1

You can add 'i' modifier that means "ignore case"

var results = new RegExp('[\\?&]' + name + '=([^&#]*)', 'i').exec(window.location.href);

Answer 2

modifiers are given as the second parameter:

new RegExp('[\\?&]' + name + '=([^&#]*)', "i")

Answer 3

Simple one liner. In the example below it replaces every vowel with an X.

function replaceWithRegex(str, regex, replaceWith) {
  return str.replace(regex, replaceWith);
}

replaceWithRegex('HEllo there', /[aeiou]/gi, 'X'); //"HXllX thXrX"

Answer 4

Just an alternative suggestion: when you find yourself reaching for "case insensitive regex", you can usually accomplish the same by just manipulating the case of the strings you are comparing:

const foo = 'HellO, WoRlD!';
const isFoo = 'hello, world!';
return foo.toLowerCase() === isFoo.toLowerCase();

I would also call this easier to read and grok the author's intent!