EncodeURI

On web sites, URLs use special syntax—for example they encode a hash sign as a character sequence "%23." Spaces can also be encoded.

In a Node.js program, we want to encode and decode URIs when we interact with the browser's location. This does not need to be done manually (except in special cases).

EncodeURIComponent

Suppose our app creates a "component" of a URL, not an entire URL. Symbols such as the hash and ampersand should be encoded, not left in their original condition.

var part = "c# bird & fish";

// The encodeURIComponent method will encode hash signs.
var result = encodeURIComponent(part);
console.log("ENCODE BEORE: " + part);
console.log("ENCODE AFTER: " + result);
ENCODE BEORE: c# bird & fish
ENCODE AFTER: c%23%20bird%20%26%20fish

EncodeURI example

This method is like encodeURIComponent but it does not encode certain chars like the hash symbol. These are left alone and considered part of the URL structure.

var part = "f# example";

// The encodeURIComponent method will not encode some things.
// ... If you want those things encoded, use encodeURIComponent.
var result = encodeURI(part);
console.log("ENCODEURI: " + result);
ENCODEURI: f#%20example

DecodeURI

This method does the opposite of encodeURI—it transforms an encoded URL back into a normal string format. We can use its decodeURIComponent counterpart.

var part = "c%23%20example";

// Use decodeURI and decodeURIComponent methods.
var result1 = decodeURI(part);
var result2 = decodeURIComponent(part);
console.log("DECODEURI: " + result1);
console.log("DECODEURICOMPONENT: " + result2);
DECODEURI: c%23 example
DECODEURICOMPONENT: c# example

Performance note

In my testing, replace() calls that replace characters globally were slower than encodeURIComponent. Three replace calls were about 3 times slower than encodeURIComponent.

Summary

It is tempting to write "replace" calls for URLs to fix their characters. This is a bad idea. With specialized methods like encodeURI we have a faster and clearer solution.