CODEWITHSUNDEEP
javascriptnode.js
GCSDC
GCSDC

Reputation: 3500

Loop through 2 number ranges on javascript

I'm developing a solution on which I need to loop through two separate continuous number ranges. Lets say for example 1 to 5 and 10 to 15.

I'm using the following code:

var X = [];

for (i = 1; i < 6; i++) {
  X.push(i);
}
for (i = 10; i < 16; i++) {
  X.push(i);
}

for (var x in X) {      
  console.log(parseInt(X[x]));
}

This code does the job, but have a lot of overhead and unnecessary operations:

Is there any simpler/more efficient way to perform this kind of operation? Something like this:

for(x = 1 to 5, then x = 10 to 15) {
  // do something with x
}

Constraints:

I've searched through SO but couldn't find any solution for this.

Thanks in advance!

Upvotes: 1

Views: 7004

Answers (3)

castletheperson
castletheperson

Reputation: 33496

In ES6 you could create some generator functions which abstract away the looping details, and use a for...of loop. This way you will have the readable syntax you're looking for, while not creating any large arrays.

function* ranges(...rangeDescriptors) {
  for (const [min, max, step = 1] of rangeDescriptors)
    for (let i = min; i < max; i += step)
      yield i;
}

for (const x of ranges([1, 6], [10, 16])) {
  console.log(x);
}

Upvotes: 3

guest271314
guest271314

Reputation: 1

You can use for..of loop, for loop, spread element 

let res = [];

for (let [from, to] of [[1, 6], [10, 16]]) 
  for (let x = from; x < to; x++) console.log(x); res.push(x);

console.log(res);

If requirement is to only log digits at console, or "// do something with x" without storing result of "something" in an array, we can reduce javascript to

for (let [from, to] of [[1, 6], [10, 16]])
  for (let x = from; x < to; x++) console.log(x); // do stuff with `x`

Upvotes: 5

fubar
fubar

Reputation: 17388

This isn't necessarily more efficient, but it does keep everything nice and tidy and prevents duplication of code.

Basically, write a function that accepts an array of ranges and a callback to be executed on each iteration of the loop through the specified ranges.

The range and current index are passed to the callback, should they be needed.

function loop(ranges, callback) {
  ranges.forEach(function (range) {
    for (var i = range[0]; i <= range[1]; i++) callback(range, i);
  });
}

var ranges = [
  [1, 5],
  [10, 15],
];

var callback = function (range, i) {
  console.log(i);
}

loop(ranges, callback);

Upvotes: 2

Related Questions