JavaScript | Encode/Decode a string to Base64
In order to encode/decode a string in JavaScript, we are using built-in functions provided by JavaScript.
btoa() Method
This method encodes a string in base-64 and uses the “A-Z”, “a-z”, “0-9”, “+”, “/” and “=” characters to encode the provided string.
Syntax:
window.btoa( String )
Parameter (String): This parameter is required. It specifies the string to be encoded.
atob() Method
This method decodes a base-64 encoded string, which has been encoded by the btoa() method.
Syntax:
window.atob( String )
Parameter (String): This parameter is required. It specifies the string which has already been encoded by the btoa() method.
Here are few of the examples.
Example 1: This examples encodes the string “This is GeeksForGeeks” by btoa() function.
Javascript
function encodeStr() { console.log(btoa(str));}const str = "This is GeeksForGeeks";encodeStr(); |
Output
VGhpcyBpcyBHZWVrc0ZvckdlZWtz
Example 2: This examples decodes the string “VGhpcyBpcyBHZWVrc0ZvckdlZWtz” encoded by btoa() function with the help of atob() function.
Javascript
function decodeStr() { console.log(atob(str));}const str = "VGhpcyBpcyBHZWVrc0ZvckdlZWtz";decodeStr(); |
Output
This is GeeksForGeeks
The Cross-Browser Method is used as a JavaScript library to encode/decode a string in any browser.
Example 3: This examples encodes the string “This is GeeksForGeeks” by creating a Base64 object.
Javascript
let Base64 = { _keyStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "abcdefghijklmnopqrstuvwxyz0123456789+/=", encode: function (e) { let t = ""; let n, r, i, s, o, u, a; let f = 0; e = Base64._utf8_encode(e); while (f < e.length) { n = e.charCodeAt(f++); r = e.charCodeAt(f++); i = e.charCodeAt(f++); s = n >> 2; o = (n & 3) << 4 | r >> 4; u = (r & 15) << 2 | i >> 6; a = i & 63; if (isNaN(r)) { u = a = 64 } else if (isNaN(i)) { a = 64 } t = t + this._keyStr.charAt(s) + this._keyStr.charAt(o) + this._keyStr.charAt(u) + this._keyStr.charAt(a) } return t }, decode: function (e) { let t = ""; let n, r, i; let s, o, u, a; let f = 0; e = e.replace(/[^A-Za-z0-9\+\/\=]/g, ""); while (f < e.length) { s = this._keyStr.indexOf(e.charAt(f++)); o = this._keyStr.indexOf(e.charAt(f++)); u = this._keyStr.indexOf(e.charAt(f++)); a = this._keyStr.indexOf(e.charAt(f++)); n = s << 2 | o >> 4; r = (o & 15) << 4 | u >> 2; i = (u & 3) << 6 | a; t = t + String.fromCharCode(n); if (u != 64) { t = t + String.fromCharCode(r) } if (a != 64) { t = t + String.fromCharCode(i) } } t = Base64._utf8_decode(t); return t }, _utf8_encode: function (e) { e = e.replace(/\r\n/g, "\n"); let t = ""; for (let n = 0; n < e.length; n++) { let r = e.charCodeAt(n); if (r < 128) { t += String.fromCharCode(r) } else if (r > 127 && r < 2048) { t += String.fromCharCode(r >> 6 | 192); t += String.fromCharCode(r & 63 | 128) } else { t += String.fromCharCode(r >> 12 | 224); t += String.fromCharCode(r >> 6 & 63 | 128); t += String.fromCharCode(r & 63 | 128) } } return t }, _utf8_decode: function (e) { let t = ""; let n = 0; let r = c1 = c2 = 0; while (n < e.length) { r = e.charCodeAt(n); if (r < 128) { t += String.fromCharCode(r); n++ } else if (r > 191 && r < 224) { c2 = e.charCodeAt(n + 1); t += String.fromCharCode( (r & 31) << 6 | c2 & 63); n += 2 } else { c2 = e.charCodeAt(n + 1); c3 = e.charCodeAt(n + 2); t += String.fromCharCode( (r & 15) << 12 | (c2 & 63) << 6 | c3 & 63); n += 3 } } return t }}function encodeStr() { console.log(Base64.encode(str));}const str = "This is GeeksForGeeks";encodeStr(); |
Output
VGhpcyBpcyBHZWVrc0ZvckdlZWtz
Example 4: This examples encodes the string “VGhpcyBpcyBHZWVrc0ZvckdlZWtz” by creating a Base64 object.
Javascript
let Base64 = { _keyStr: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef" + "ghijklmnopqrstuvwxyz0123456789+/=", encode: function (e) { let t = ""; let n, r, i, s, o, u, a; let f = 0; e = Base64._utf8_encode(e); while (f < e.length) { n = e.charCodeAt(f++); r = e.charCodeAt(f++); i = e.charCodeAt(f++); s = n >> 2; o = (n & 3) << 4 | r >> 4; u = (r & 15) << 2 | i >> 6; a = i & 63; if (isNaN(r)) { u = a = 64 } else if (isNaN(i)) { a = 64 } t = t + this._keyStr.charAt(s) + this._keyStr.charAt(o) + this._keyStr.charAt(u) + this._keyStr.charAt(a) } return t }, decode: function (e) { let t = ""; let n, r, i; let s, o, u, a; let f = 0; e = e.replace(/[^A-Za-z0-9\+\/\=]/g, ""); while (f < e.length) { s = this._keyStr.indexOf(e.charAt(f++)); o = this._keyStr.indexOf(e.charAt(f++)); u = this._keyStr.indexOf(e.charAt(f++)); a = this._keyStr.indexOf(e.charAt(f++)); n = s << 2 | o >> 4; r = (o & 15) << 4 | u >> 2; i = (u & 3) << 6 | a; t = t + String.fromCharCode(n); if (u != 64) { t = t + String.fromCharCode(r) } if (a != 64) { t = t + String.fromCharCode(i) } } t = Base64._utf8_decode(t); return t }, _utf8_encode: function (e) { e = e.replace(/\r\n/g, "\n"); let t = ""; for (let n = 0; n < e.length; n++) { let r = e.charCodeAt(n); if (r < 128) { t += String.fromCharCode(r) } else if (r > 127 && r < 2048) { t += String.fromCharCode(r >> 6 | 192); t += String.fromCharCode(r & 63 | 128) } else { t += String.fromCharCode(r >> 12 | 224); t += String.fromCharCode(r >> 6 & 63 | 128); t += String.fromCharCode(r & 63 | 128) } } return t }, _utf8_decode: function (e) { let t = ""; let n = 0; let r = c1 = c2 = 0; while (n < e.length) { r = e.charCodeAt(n); if (r < 128) { t += String.fromCharCode(r); n++ } else if (r > 191 && r < 224) { c2 = e.charCodeAt(n + 1); t += String.fromCharCode( (r & 31) << 6 | c2 & 63); n += 2 } else { c2 = e.charCodeAt(n + 1); c3 = e.charCodeAt(n + 2); t += String.fromCharCode( (r & 15) << 12 | (c2 & 63) << 6 | c3 & 63); n += 3 } } return t }}function decodeStr() { console.log(Base64.decode(str));}const str = "VGhpcyBpcyBHZWVrc0ZvckdlZWtz";decodeStr(); |
Output
This is GeeksForGeeks
