How to generate sequence of numbers/chars in javascript?

Question

Is there a way to generate sequence of characters or numbers in javascript?

For example, I want to create array that contains eight 1s. I can do it with for loop, bu

Answer 1

If you want to produce a sequence of equal numbers, this is an elegant function to do it (solution similar to other answer):

seq = (n, value) => Array(n).fill(value)

If you want to produce a sequence of consecutive numbers, beginning with 0, this a nice oneliner:

seq = n => n<1 ? [] : [0, ...seq(n-1).map(v => v+1)]

It can easily extended for different start values and increments:

seq = (n, start=0, inc=1) => n<1 ? [] : [start, ...seq(n-1, start, inc).map(v => v+inc)]

Answer 2

Why not just a simple join and split?

function seq(len, value)
{
    // create an array
    // join it using the value we want
    // split it
    return (new Array(len + 1)).join(value).split("");
}

seq(10, "a");
["a", "a", "a", "a", "a", "a", "a", "a", "a", "a"]

seq(5, 1);
["1", "1", "1", "1", "1"]

Answer 3

2016 - Modern Browser functionality has arrived. No need for jquery all the time.

Array.from({length: 8}, (el, index) => 1 /* or index */);

You can substitute the arrow function with a simple callback function to reach a slightly wider range of supported browsers. It's, for me at least, the easiest way to iterate over an initialized array in one step.

Note: IE is not supported in this solution, but there is a polyfill for that at developer.mozilla.org/...

Answer 4

Another method, for those how are memory saving pedant:

Array.apply(null, Array(3)).map(Function.prototype.call.bind(Number))

Answer 5

for (var i=8, a=[]; i--;) a.push(1);

Answer 6

You can make your own re-usable function I suppose, for your example:

function makeArray(count, content) {
   var result = [];
   if(typeof content == "function") {
      for(var i = 0; i < count; i++) {
         result.push(content(i));
      }
   } else {
      for(var i = 0; i < count; i++) {
         result.push(content);
      }
   }
   return result;
}

Then you could do either of these:

var myArray = makeArray(8, 1);
//or something more complex, for example:
var myArray = makeArray(8, function(i) { return i * 3; });

You can give it a try here, note the above example doesn't rely on jQuery at all so you can use it without. You just don't gain anything from the library for something like this :)