Question

In prototype the cumbersome for:

for (i=0; i<10; i++) { ... }

can be written as

$R(0, 10).each(function(i){ ... });

Is there an equivalent of range in JQuery ?

Answer 1

See http://code.google.com/p/jquery-utils/source/browse/trunk/src/jquery.arrayUtils.js?r=452

jQuery does not provide range expansion natively, but it’s an easy addition. There are only two parts to it. First the range function should return an array with the each item in the range expanded to an array value. Next add a method to Array to iterate each object passing in a handler function.

Here we define forEach that’s part of the ECMA-262 standard for iterating over arrays. See MDC for more details.

if (!Array.prototype.forEach) {
  Array.prototype.forEach = function(fun /*, thisp*/) {
    var len = this.length >>> 0;
    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);
    }
  };
}

Next, we need a function to expand ranges to an array within the jQuery namespace. Taken from the above URL (original source – http://blog.outofhanwell.com/2006/03/29/javascript-range-function/)
:

$.extend({
    // Returns a range object
    // Author: Matthias Miller
    // Site:   http://blog.outofhanwell.com/2006/03/29/javascript-range-function/
    range:  function() {
        if (!arguments.length) { return []; }
        var min, max, step;
        if (arguments.length == 1) {
            min  = 0;
            max  = arguments[0]-1;
            step = 1;
        }
        else {
            // default step to 1 if it's zero or undefined
            min  = arguments[0];
            max  = arguments[1]-1;
            step = arguments[2] || 1;
        }
        // convert negative steps to positive and reverse min/max
        if (step < 0 && min >= max) {
            step *= -1;
            var tmp = min;
            min = max;
            max = tmp;
            min += ((max-min) % step);
        }
        var a = [];
        for (var i = min; i <= max; i += step) { a.push(i); }
        return a;
    }
});

Alrighty, now we can do:

$.range(2, 10).forEach(function(v) {
    console.log(v); // 2, 3, 4, .., 9
});

Or use it with a custom step value instead of 1

$.range(2, 20, 4).forEach(function(v) {
    console.log(v); // 2, 6, 10, 14, 18
});