CODEWITHSUNDEEP
javascriptextjsfunctional-programmingextjs4.1
Nadav
Nadav

Reputation: 1185

How to run a function on each of array elements in Javascript

I wish to run a function that exists on each of my array's elements.
I know it can be done with a for loop, an each, and map, but none of these pursue a pure functional approach. for example, with map it would look something like this:
var a = [1,2,3].map(function(item) { item.funcName(params); });

I do not care about the return values of these functions

example code I wish I had:
var a = [1,2,3].magicRun('funcName'[, paramsArray]);;

Is there such a thing in pure JS? It there such a thing in ExtJS? (which I have avail. loaded ver. 4.1)

Thanks!

Upvotes: 0

Views: 4162

Answers (3)

Hikari
Hikari

Reputation: 3947

if (!Array.prototype.forEach)
{
  Array.prototype.forEach = function(fun /*, thisp*/)
  {
    var len = this.length;
    if (typeof fun != "function")
      throw new TypeError();

    var thisp = arguments[1];
    for (var i = 0; i < len; i++)
    {
      if (i in this)
        fun.call(thisp, this[i], i, this);
    }
  };
}

exemple:

<html>
<head>
<title>JavaScript Array forEach Method</title>
</head>
<body>
<script type="text/javascript">
if (!Array.prototype.forEach)
{
  Array.prototype.forEach = function(fun /*, thisp*/)
  {
    var len = this.length;
    if (typeof fun != "function")
      throw new TypeError();

    var thisp = arguments[1];
    for (var i = 0; i < len; i++)
    {
      if (i in this)
        fun.call(thisp, this[i], i, this);
    }
  };
}

function printBr(element, index, array) {
  document.write("<br />[" + index + "] is " + element ); 
}

[12, 5, 8, 130, 44].forEach(printBr);

</script>
</body>
</html>

source: http://www.tutorialspoint.com/javascript/array_foreach.htm

Upvotes: 0

Rob Agar
Rob Agar

Reputation: 12459

There's nothing exactly like what you want in pure JS, and I don't think ExtJS has it either (but I haven't used ExtJS in anger since version 3.something, so there might be)

MooTools however adds this invoke method to Array:

invoke: function(methodName){
  var args = Array.slice(arguments, 1);
  return this.map(function(item){
    return item[methodName].apply(item, args);
  });
},

...which being released under the MIT license, you can lift without any bad karma

Upvotes: 1

Javier Cobos
Javier Cobos

Reputation: 1182

In pure Js you can add the function "map" to Array object prototype

In this example I make the sqrt of every element of the array

if (!Array.prototype.map)
    Array.prototype.map = function(fun)
    {
        var len = this.length;
        if (typeof fun != "function")
            throw new TypeError();
        var res = new Array(len);
        for (var i = 0; i < len; ++i)
            res[i] = fun(this[i]);
        return res;
};


var numbers = [1, 4, 9];
var roots = numbers.map(Math.sqrt);

//could be an alert
console.log("roots is : " + roots );

Upvotes: 2

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