Reindexing an array

Question

Here is my example.

Can you tell me how can I make the array have consecutive keys? I want to reindex my array.

Currently I have:

var testArray = new Array();
testArray[3]="qwerty";
testArray[7]="asdfgh";
testArray[13]="zxcvbn";

console.log(testArray);

But I'd like to get the values at indices 0, 1 and 2 (and so on):

["qwerty", "asdfgh", "zxcvbn"]

Answer 1

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)

Answer 2

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;
  };
}

Answer 3

You could filter the array by using a callback which returns true or other truthy value, because Array#filter omits sparse elements.

If Boolean is taken, the result filters not only sparse items, but items which have a falsy value. To prevent this, take a callback which returns true for every element.

array.filter(_ => true);

var array = [];

array[10] = 0;
array[20] = 0;
array[30] = 0;

console.log(array.filter(_ => true).join('|'))

Answer 4

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

Answer 5

var testArray = new Array();
testArray[3] = "qwerty";
testArray[7] = "asdfgh";
testArray[13] = "zxcvbn";


var isEmpty = function(x) {
   // returns true if x is null and false if it is not.
    if(x!=null){ 
        return true;
    }else{ 
        return false
    } 
}
var newArray=testArray.filter(isEmpty);

var testString2 = newArray.join();

$('#write').text(testString2);