Javascript - Reindexing an array

Array.prototype.filter() is not executed on deleted or previously undefined items. So you can simply do:

testArray.filter(function(val){return val});

..in order to re-index your array.

Or ES6:

testArray.filter(val => val)

If you don't mind using javascript 1.6: (note: this code uses the jQUery library)

var testArray = new Array();
testArray[3]="qwerty";
testArray[7]="asdfgh";
testArray[13]="zxcvbn";
var testString = testArray.filter(function (item) { return item != undefined }).join();

$(function(){
    $('#write').text(testString);
});

filter prototype:

if (!Array.prototype.filter)
{
  Array.prototype.filter = function(fun /*, thisp */)
  {
    "use strict";

    if (this === void 0 || this === null)
      throw new TypeError();

    var t = Object(this);
    var len = t.length >>> 0;
    if (typeof fun !== "function")
      throw new TypeError();

    var res = [];
    var thisp = arguments[1];
    for (var i = 0; i < len; i++)
    {
      if (i in t)
      {
        var val = t[i]; // in case fun mutates this
        if (fun.call(thisp, val, i, t))
          res.push(val);
      }
    }

    return res;
  };
}

Super simple function:

function reindex_array_keys(array, start){
    var temp = [];
    start = typeof start == 'undefined' ? 0 : start;
    start = typeof start != 'number' ? 0 : start;
    for(var i in array){
        temp[start++] = array[i];
    }
    return temp;
}
testArray = reindex_array_keys(testArray);

Note: this will blow away any custom keys. the result will always be numerically indexed. you could add in checks for if it's an array or not but i tend to just not use functions i build other than they are intended to be used. you can also start the index higher if you like:

testArray = reindex_array_keys(testArray, 3);

which will produce 3 'undefined' items at the beginning of the array. you can then add to it later but i think it would be better to do testArray.unshift('newValue') first then reindex personally.

have fun