Strings (in JavaScript)

Removing suffix or prefix from string

To remove the end of a string from a regular string, the general solution is String.slice.

const fruit = "apple";

// Remove a suffix - "app"
fruit.slice(0, 2);

// Remove a prefix - "le"
fruit.slice(-2);

If specifically trimming whitespace, it'd be better to use the String.prototype.trim() function.

const fruit = "       apple      ";

// "apple";
fruit.trim();
// Note that after this point, the original string is NOT modified.

String.prototype.includes

Checks if a given string contains a given substring.

Usage:

const name = "Joseph Maguire";

// true
name.includes("Joseph");

// false, as the search is case-sensitive.
name.includes("mag");

// true
name.toLowerCase().includes("mag");

String.prototype.replace

The replace() method on a string replaces a given substring with a new one. It returns a new string and does not mutate the old one.

const fruit = "banana";

// "banena"
// Given a string, will only edit the first find.
fruit.replace("na", "ne");

// "banene"
// Given a global regex, will edit all.
fruit.replace(/na/g, "ne");

// "The%20Night%20Before%20Christmas"
"The Night Before Christmas".replace(/\s/g, "%20");

Convert a string into an array of specified lengths

The easiest way to do this is to use the .match() regex function.

Note

This will only work if all the groups are the same length.**

const fruit = "apple";

// Read the pattern as 'wildcards of length either 2 or 1'.
// [ "ap", "pl", "e" ]
const bits = fruit.match(/.{2,1}/g);

However, if you require the lengths to be different each time, then you can use String.prototype.split().

const fruit = "apple";

// [ "", "a", "ppl", "e", "" ]
const bits = fruit.split(/(.{1})(.{3})(.{1}))/g);

It may be better to be less 'super efficient' here and break things up into explicit string lengths instead.