Convert character to ASCII code in JavaScript

String.prototype.charCodeAt() can convert string characters to ASCII numbers. For example:

"ABC".charCodeAt(0) // returns 65

For opposite use String.fromCharCode(10) that convert numbers to equal ASCII character. This function can accept multiple numbers and join all the characters then return the string. Example:

String.fromCharCode(65,66,67); // returns 'ABC'

Here is a quick ASCII characters reference:

{
"31": "",    "32": " ",    "33": "!",    "34": "\"",    "35": "#",    
"36": "$",    "37": "%",    "38": "&",    "39": "'",    "40": "(",    
"41": ")",    "42": "*",    "43": "+",    "44": ",",    "45": "-",    
"46": ".",    "47": "/",    "48": "0",    "49": "1",    "50": "2",    
"51": "3",    "52": "4",    "53": "5",    "54": "6",    "55": "7",    
"56": "8",    "57": "9",    "58": ":",    "59": ";",    "60": "<",    
"61": "=",    "62": ">",    "63": "?",    "64": "@",    "65": "A",    
"66": "B",    "67": "C",    "68": "D",    "69": "E",    "70": "F",    
"71": "G",    "72": "H",    "73": "I",    "74": "J",    "75": "K",    
"76": "L",    "77": "M",    "78": "N",    "79": "O",    "80": "P",    
"81": "Q",    "82": "R",    "83": "S",    "84": "T",    "85": "U",    
"86": "V",    "87": "W",    "88": "X",    "89": "Y",    "90": "Z",    
"91": "[",    "92": "\\",    "93": "]",    "94": "^",    "95": "_",    
"96": "`",    "97": "a",    "98": "b",    "99": "c",    "100": "d",    
"101": "e",    "102": "f",    "103": "g",    "104": "h",    "105": "i",    
"106": "j",    "107": "k",    "108": "l",    "109": "m",    "110": "n",    
"111": "o",    "112": "p",    "113": "q",    "114": "r",    "115": "s",    
"116": "t",    "117": "u",    "118": "v",    "119": "w",    "120": "x",    
"121": "y",    "122": "z",    "123": "{",    "124": "|",    "125": "}",    
"126": "~",    "127": ""
}

If you have only one char and not a string, you can use:

var a = 'A';
var codeA = a.charCodeAt();

omitting the 0...

While the other answers are right, I prefer this way:

function ascii (a) { return a.charCodeAt(0); }

Then, to use it, simply:

var lineBreak = ascii("\n");

I am using this for a small shortcut system:

$(window).keypress(function(event) {
  if (event.ctrlKey && event.which == ascii("s")) {
    savecontent();
    }
  // ...
  });

And you can even use it inside map() or other methods:

var ints = 'ergtrer'.split('').map(ascii);

For those that want to get a sum of all the ASCII codes for a string:

'Foobar'
  .split('')
  .map(function (char) {
    return char.charCodeAt(0);
  })
  .reduce(function (current, previous) {
    return previous + current;
  });

Or, ES6:

[...'Foobar']
  .map(char => char.charCodeAt(0))
  .reduce((current, previous) => previous + current)

For supporting all UTF-16 (also non-BMP/supplementary characters) from ES6 the string.codePointAt() method is available;

This method is an improved version of charCodeAt which could support only unicode codepoints < 65536 ( 2¹⁶ - a single 16bit ) .

I found this open source function inside the javascript-algorithms library:

function convertToAscii(str) {
  var result = '';
  var currentChar = '';
  var i = 0;
  for (; i < str.length; i += 1) {
    currentChar = str[i].charCodeAt(0).toString(2);
    if (currentChar.length < 8) {
      while (8 - currentChar.length) {
        currentChar = '0' + currentChar;
      }
    }
    result += currentChar;
  }
  return result;
}