One line Array iterator javascript-CodePudding

I am coming from Python and I am looking for a single line iterator function for any array, where I can also check a condition and return a simple change to the items.

Expected result should match the method:

function arrayEvenItemIncrement(myArray){
    for (let i = 0; i < myArray.length; i  ){
        if (myArray[i]%2==0){
            myArray[i]  ;
        }
    }
    return myArray;
}

I tried using for (i of myArray){ } but this still doesn't serve my purpose.

CodePudding user response：

I think the clearest way to do what you want here would be to map to a new array instead of mutating the old one:

const arrayEvenItemIncrement = myArray =>
  myArray.map((val, i) => i % 2 === 1 ? val : val   1);

If you have to mutate the existing array, it gets significantly uglier.

const arrayEvenItemIncrement = myArray => (
  myArray.forEach((val, i) => { if (i % 2 === 0) myArray[i]  ; }), myArray);

const arrayEvenItemIncrement = myArray => {
  myArray.forEach((val, i) => { if (i % 2 === 0) myArray[i]  ; }); return myArray };

But I wouldn't recommend that - put it on multiple lines instead.

You can technically squeeze any JS code into a single line, but past simple manipulations, it usually isn't a good idea because it sacrifices readability, which is far more important than reducing LoC. Professional, maintainable code is not a golfing competition.

CodePudding user response：

The Array method .reduce(prv, cur, idx, arr) is perfect for shrinking an array of values into a single value. The main function of the example below, countEven(arr), is at it's core is a simple callback which is just a basic ternary (ie if/else as an expression). The counting is streamlined as well -- it relies on the first argument of .reduce(): prv (in the example it is cnt) to increment by 1 on every iteration in that there's a number with even parity. Normally, a counter would require operating in nested functions, implementing a closure, etc.

Details are commented in example

/** FOR DEMO ONLY - NOT REQUIRED
 ** log(anyValue) formats
 ** console.log for readability.
 */
const log = data => console.log(JSON.stringify(data));
/** FOR DEMO ONLY - NOT REQUIRED
 ** genArr(arrLength, 100)
 ** returns an array of random
 ** numbers. Array length 
 ** is required and max value 
 ** is optional (defaults to 100)
 */
const genArr = (len, max = 100) => new Array(len).fill(0).map(o => Math.floor(Math.random() * max));

/** countEven(arr) returns a
 ** count of all even parity
 ** numbers of a given array
 ** of numbers.
 */
const countEven = arr => arr.reduce((cnt, cur) => cur === 0 || cur % 2 === 1 ? cnt : cnt   1, 0);

/** In the callback, cnt is 
 ** incremented when cur is even.
 */

let test = genArr(30);
log(test);
log(countEven(test));

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