Utility functions for implementing a PKCE authorization flow in browsers.

pkce_utility.js

// Utility functions
function base64url_encode(string) {
    return btoa(string).replace(/\+/g, "-").replace(/\//g, "_").replace(/=/g, "");
}

function base64url_decode(string) {
    return atob(string.replace(/-/g, "+").replace(/_/g, "/"));
}

function random_string(bytes) {
    return String.fromCharCode(...crypto.getRandomValues(new Uint8Array(bytes)));
}

async function sha_256(string) {
    return String.fromCharCode(...new Uint8Array(await crypto.subtle.digest("SHA-256", new TextEncoder().encode(string))));
}