I have an array that looks like:
var myArray = [12, 24, 36, 48, 60, 15, 30];
I need to build a new array of arrays from this to show the index number from the original array in the new array. The final result should look like the following:
var myNewArray = [
[1, 12],
[2, 24],
[3, 36],
[4, 48],
[5, 60],
[6, 15],
[7, 30]
];
You can use Array.prototype.map(), and then generate new array based on value and index of that array.
var myArray = [12, 24, 36, 48, 60, 15, 30],
newArray = myArray.map(function (value, index) {
return [index + 1, value];
});
FYI: - JavaScript arrays are zero-indexed: the first element of an array is at index 0
var myArray= [12, 24, 36, 48, 60, 15, 30],
myArrayIndexed= myArray.map(function(itm, i){
return [i+1, itm];
});
myArrayIndexed.join(']\n[');
/* returned value: */ [
[1, 12],
[2, 24],
[3, 36],
[4, 48],
[5, 60],
[6, 15],
[7, 30]
]
It's as simple as that:
var myArray = [12, 24, 36, 48, 60, 15, 30];
var myNewArray = [];
for (var i = 0; i < myArray.length; i++) {
myNewArray.push([i+1,myArray[i]]);//or just i depending on the index you need
}
Even a faster way is to cache the length of the array:
for (var i = 0, var l = myArray.length; i < l; i++) {}
To my knowledge and research so far - Javascript's native for loop is quicker than array map for iterating through the array. Here is an interesting benchmark.
Hope this helps!
