CODEWITHSUNDEEP
javascriptarraysfor-loop
artworkjpm
artworkjpm

Reputation: 1337

make an array of arrays from for loop

I want to put each iteration into an array which is in a main array. Like this: array = [[a,b], [c,d], [e,f]]

push method and slice, splice

var descendants = [A,C,C,D,C,B], 
chunk = 2, 
descendantPairs = [];
for (var i = 0; i < descendants.length; i += chunk) {
descendantPairs = descendantPairs.push(descendants.slice(i, i + chunk));
console.log("descendantPairs: " + descendantPairs});
}

Right now I'm able to get the pairs like this but I need to do more logic on ALL the pairs, instead of just the last pair, therefore I need an array which holds all the pairs.

I get this now in console.log:

descendantPairs: A,C descendantPairs: C,D descendantPairs: C,B

Upvotes: 1

Views: 1245

Answers (6)

Code Maniac
Code Maniac

Reputation: 37755

You can use a simple for loop and a temp variable and push values on every second index to final output

var arr = [`A`,`C`,`C`,`D`,`C`,`B`]
let op = []
let temp = []

for(let i = 0; i < arr.length; i++){
  temp.push(arr[i])
  if( i % 2 == 1 ){
    op.push(temp)
    temp = []
  }
}
if( temp.length > 0 ){
  op.push(temp)
}

console.log(op)

Upvotes: 1

Moad Ennagi
Moad Ennagi

Reputation: 1073

var arr = ['A','C','C','D','C','B'];
let chunk = 2;
let pairs = [];

for(let i = 0; i < arr.length; i+= chunk) {
    pairs.push(arr.slice(i, i + chunk));
}
console.log(pairs);

Upvotes: -1

Nina Scholz
Nina Scholz

Reputation: 386578

You could push each slice to the result array, without assining the new length of the array. The next loop throws an error, because your descendantPairs is now a number and not anymore an array, which is needed for using the push method.

var descendants = ['A', 'C', 'C', 'D', 'C', 'B'],
    chunk = 2,
    result = [],
    i = 0;

while (i < descendants.length) {
    result.push(descendants.slice(i, i += chunk));
}
console.log(result);

Upvotes: 1

Miroslav Glamuzina
Miroslav Glamuzina

Reputation: 4557

Something like this will do the trick:

let descendants = ['A', 'C', 'C', 'D', 'C', 'B'];
let chunk = 2;
let result = [];

for (let i = 0; i < descendants.length; i += chunk) {
  result.push(descendants.slice(i, i+chunk));
}
console.log(result);

Upvotes: 1

Pranav C Balan
Pranav C Balan

Reputation: 115222

Your code contains one issue, you are reassigning descendantPairs with returned value of Array#push method which will be the length of the array and it leads to throwing an error on the next iteration(since there is no push method for type Number).

To make it work just remove the reassigning part and log the value after the for loop.

var descendants = ['A', 'C', 'C', 'D', 'C', 'B'],
  chunk = 2,
  descendantPairs = [];

for (var i = 0; i < descendants.length; i += chunk) {
  descendantPairs.push(descendants.slice(i, i + chunk));
}

console.log("descendantPairs: ", descendantPairs);

Upvotes: 1

Sandeep Polamuri
Sandeep Polamuri

Reputation: 609

The push method returns the length of the added element, not the array after pushing the element.

replace descendantPairs = descendantPairs.push(descendants.slice(i, i + chunk)); with

descendantPairs.push(descendants.slice(i, i + chunk));

Upvotes: 2

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