javascript - Create Simple Dynamic Array

Question

What\'s the most efficient way to create this simple array dynamically.

var arr = [ \"1\", \"2\", \"3\", \"4\", \"5\", \"6\", \"7\", \"8\", \"9\", \"10\"];
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Answer 1

var arr = [];
while(mynumber--) {
    arr[mynumber] = String(mynumber+1);
}

Answer 2

The same way you would for all arrays you want to fill dynamically. A for loop. Suedo code is

arr =array()
for(i; i<max; i++){
 arr[]=i

}

that should help you on the way

Answer 3

Some of us are referring to use from which is not good at the performance:

function getArrayViaFrom(input) {
  console.time('Execution Time');
  let output = Array.from(Array(input), (value, i) => (i + 1).toString())
  console.timeEnd('Execution Time');

  return output;
}

function getArrayViaFor(input) {
  console.time('Execution Time 1');
  var output = [];
  for (var i = 1; i <= input; i++) {
    output.push(i.toString());
  }
  console.timeEnd('Execution Time 1');

  return output;
}

console.log(getArrayViaFrom(10)) // Takes 10x more than for that is 0.220ms
console.log(getArrayViaFor(10))  // Takes 10x less than From that is 0.020ms

Answer 4

var arr = [];
for(var i=1; i<=mynumber; i++) {
   arr.push(i.toString());
}

Answer 5

This answer is about "how to dynamically create an array without loop".

Literal operator [] doesn't allow us to create dynamically, so let's look into Array, it's constructor and it's methods.

In ES2015 Array has method .from(), which easily allows us to create dynamic Array:

Array.from({length: 10}) // -> [undefined, undefined, undefined, ... ]

When Array's constructor receives number as first parameter, it creates an Array with size of that number, but it is not iterable, so we cannot use .map(), .filter() etc. :

new Array(10) // -> [empty × 10]

But if we'll pass more than one parameter we will receive array from all parameters:

new Array(1,2,3) // -> [1,2,3]

If we would use ES2015 we can use spread operator which will spread empty Array inside another Array, so we will get iterable Array :

[...new Array(10)]  // -> [undefined, undefined, undefined, ...]

But if we don't use ES2015 and don't have polyfills, there is also a way to create dynamic Array without loop in ES5. If we'll think about .apply() method: it spreads second argument array to params. So calling apply on Array's constructor will do the thing:

Array.apply(null, new Array(10))  // -> [undefined, undefined, undefined, ...]

After we have dynamic iterable Array, we can use map to assign dynamic values:

Array.apply(null, new Array(10)).map(function(el, i) {return ++i + ""})

// ["1","2","3", ...]

Answer 6

I would do as follows;

var num = 10,
  dynar = [...Array(num)].map((_,i) => ++i+"");
console.log(dynar);