Here is an array that I am working with:
var myArray = [12, 24, 36, 48, 60, 15, 30];
I am trying to create a new array of arrays that includes the index numbers from the original array in the new array. The final result should be formatted like this:
var myNewArray = [
[1, 12],
[2, 24],
[3, 36],
[4, 48],
[5, 60],
[6, 15],
[7, 30]
];
Utilizing Array.prototype.map(), you can create a new array by taking into account the value and index of the original array.
var myArray = [12, 24, 36, 48, 60, 15, 30],
newArray = myArray.map(function (value, index) {
return [index + 1, value];
});
Just a heads-up: JavaScript arrays start at index 0, meaning the first element is at index 0.
let numbers = [12, 24, 36, 48, 60, 15, 30],
indexedNumbers = numbers.map(function(item, index){
return [index+1, item];
});
indexedNumbers.join(']\n[');
/* The resulting array is: */ [
[1, 12],
[2, 24],
[3, 36],
[4, 48],
[5, 60],
[6, 15],
[7, 30]
]
It really is that straightforward:
let myNumbers = [12, 24, 36, 48, 60, 15, 30];
let myNewNumbers = [];
for (let i = 0; i < myNumbers.length; i++) {
myNewNumbers.push([i+1, myNumbers[i]]);//you can also just use i depending on the index you want
}
You can make it even faster by storing the length of the array:
for (let i = 0, let len = myNumbers.length; i < len; i++) {}
Based on my findings and research - Javascript's built-in for loop outperforms array map when it comes to iterating through arrays. You can check out this interesting benchmark here.
I hope this information is helpful!
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