Answers for "array.from foreach javascript"

javascript foreach

const avengers = ['thor', 'captain america', 'hulk'];
avengers.forEach((item, index)=>{
	console.log(index, item)
})

javascript foreach

var colors = ['red', 'blue', 'green'];

colors.forEach(function(color) {
  console.log(color);
});

For-each over an array in JavaScript

/** 1. Use forEach and related */
var a = ["a", "b", "c"];
a.forEach(function(entry) {
    console.log(entry);
});

/** 2. Use a simple for loop */
var index;
var a = ["a", "b", "c"];
for (index = 0; index < a.length; ++index) {
    console.log(a[index]);
}

/**3. Use for-in correctly*/
// `a` is a sparse array
var key;
var a = [];
a[0] = "a";
a[10] = "b";
a[10000] = "c";
for (key in a) {
    if (a.hasOwnProperty(key)  &&        // These checks are
        /^0$|^[1-9]\d*$/.test(key) &&    // explained
        key <= 4294967294                // below
        ) {
        console.log(a[key]);
    }
}

/** 4. Use for-of (use an iterator implicitly) (ES2015+) */
const a = ["a", "b", "c"];
for (const val of a) {
    console.log(val);
}

/** 5. Use an iterator explicitly (ES2015+) */
const a = ["a", "b", "c"];
const it = a.values();
let entry;
while (!(entry = it.next()).done) {
    console.log(entry.value);
}

javascript .foreach

let colors = ['red', 'blue', 'green'];
// idx and sourceArr optional; sourceArr == colors
colors.forEach(function(color, idx, sourceArr) {
	console.log(color, idx, sourceArr)
});
// Output:
// red 0 ['red', 'blue', 'green']
// blue 1 ['red', 'blue', 'green']
// green 2 ['red', 'blue', 'green']

forEach

const arraySparse = [1,3,,7]
let numCallbackRuns = 0

arraySparse.forEach((element) => {
  console.log(element)
  numCallbackRuns++
})

console.log("numCallbackRuns: ", numCallbackRuns)

// 1
// 3
// 7
// numCallbackRuns: 3
// comment: as you can see the missing value between 3 and 7 didn't invoke callback function.

javascript foreach

const colors = ['blue', 'green', 'white'];

function iterate(item) {
  console.log(item);
}

colors.forEach(iterate);
// logs "blue"
// logs "green"
// logs "white"