I have an array and I create an another array with Array.prototype.map(). How can I console log the x value (the current element being processed in the array) during the map function?

const array1 = [1, 4, 9, 16];
const map1 = array1.map((x) => x * 2);

I have an array and I create an another array with Array.prototype.map(). How can I console log the x value (the current element being processed in the array) during the map function?

const array1 = [1, 4, 9, 16];
const map1 = array1.map((x) => x * 2);

• javascript
• arrays
• dictionary

Share Improve this question Follow edited Jan 6 at 9:49 ahuemmer 2,0591313 gold badges2727 silver badges3636 bronze badges asked Jun 19, 2021 at 9:55 Milán NikolicsMilán Nikolics 62122 gold badges1010 silver badges2424 bronze badges 5

• Use {} to create a block, instead of doing an implicit return => – PsyGik Commented Jun 19, 2021 at 10:00
• Don't use arrow functions if you don't know how they work: MDN: Arrow function expressions – Andreas Commented Jun 19, 2021 at 10:00
• 1 @PsyGik "Use {} to create a closure" - That's a block and not a "closure" – Andreas Commented Jun 19, 2021 at 10:01
• I get -1 but my qestion but have legitimate. My question is very clear. For my aspect have resarch and effort, and answer for me was super useful. Thank you again. – Milán Nikolics Commented Jun 26, 2021 at 19:15
• Yes, thank you again. Somebody else also give me +1 and other senior also answer for me but ... – Milán Nikolics Commented Jun 27, 2021 at 11:32

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5 Answers 5

Sorted by: Reset to default 3

You can use console.log in a map like this:

const array1 = [1, 4, 9, 16];
const map1 = array1.map((x) => {
  console.log(x);
  return x * 2;
});

You are using a shorthand return:

() => x returns x just as () => { return x; }.

But since you are not only returning something you can not use the concise arrow function syntax.

you can use like this:

const array1 = [1, 4, 9, 16];
const map1 = array1.map(function(x){
   console.log(x);
   return x* 2;
});

You can print it like below.

array1.map(function(x) {
      console.log(x*2);
      return x * 2
});   

const array1 = [1, 4, 9, 16];
const map1 = array1.map(function(x) {
      console.log(x*2);
      return x * 2
});

You can use an array:

const array1 = [1, 4, 9, 16];

console.log('Mapping array1...');
const map1 = array1.map((x) => [x * 2, console.log(x)][0]);
console.log('Maped successfully, map1 =', map1);

Use {} to create a block

const array1 = [1, 4, 9, 16];
const map1 = array1.map((x) => {
  console.log(x)
  return x * 2
});