For space-character removal use

"hello world".replace(/\s/g, "");

for all white space use the suggestion by Rocket in the comments below!

• To remove items from an array, splice requires you to specify how many to remove, in the second argument
• splice will remove the item at the given index from the array, so on the next iteration, if you're iterating through indicies in ascending order, you may "skip" an item, due to its index having just been re-calculated

Easier to use .pop (remove from end) and .shift (remove from beginning).

const stringWithManyWhiteSpaces = '        I like ants... Remember us   ';

function killLeftToRight(charArr) {
    while (charArr[0] === ' ') {
        charArr.shift();
    }
}

function killRightToLeft(charArr) {
    while (charArr[charArr.length - 1] === ' ') {
        charArr.pop();
    }
}

function myTrim(str){
  const charArray = [...str];
  killRightToLeft(charArray);
  killLeftToRight(charArray);
  console.log(charArray.join(''));
}

myTrim(stringWithManyWhiteSpaces);

This?

str = str.replace(/\s/g, '');

Example

var str = '/var/www/site/Brand new document.docx';

document.write( str.replace(/\s/g, '') );

Update: Based on this question, this:

str = str.replace(/\s+/g, '');

is a better solution. It produces the same result, but it does it faster.

The Regex

\s is the regex for "whitespace", and g is the "global" flag, meaning match ALL \s (whitespaces).

A great explanation for + can be found here.

As a side note, you could replace the content between the single quotes to anything you want, so you can replace whitespace with any other string.

You have to tell replace() to repeat the regex:

.replace(/ /g,'')

The g character makes it a "global" match, meaning it repeats the search through the entire string. Read about this, and other RegEx modifiers available in JavaScript here.

If you want to match all whitespace, and not just the literal space character, use \s instead:

.replace(/\s/g,'')

You can also use .replaceAll if you're using a sufficiently recent version of JavaScript, but there's not really any reason to for your specific use case, since catching all whitespace requires a regex, and when using a regex with .replaceAll, it must be global, so you just end up with extra typing:

.replaceAll(/\s/g,'')