get index from for in loop javascript code example

Example 1: for of get index

for (const v of ['a', 'b', 'c']) {
  console.log(v)
}

// get index
for (const [i, v] of ['a', 'b', 'c'].entries()) {
  console.log(i, v)
}

Example 2: javascript enumerate with index

const iterable = [...];
for (const [index, elem] in iterable.entries()) {
  f(index, elem);
}

// or
iterable.forEach((elem, index) => {
  f(index, elem);
});

Example 3: javascript for of index

let array = ["foo", "bar"]

let low = 0; // the index to start at
let high = array.length; // can also be a number

/* high can be a direct access too
	the first part will be executed when the loop starts 
    	for the first time
	the second part ("i < high") is the condition 
    	for it to loop over again.
    the third part will be executen every time the code 
        block in the loop is closed.
*/ 
for(let i = low; i < high; i++) { 
  // the variable i is the index, which is
  // the amount of times the loop has looped already
  console.log(i);
  console.log(array[i]); 
} // i will be incremented when this is hit.

// output: 
/*
	0
    foo
    1
    bar
*/

Example 4: javascript for loop return index

const targetindex = myarray.findIndex(item => item.name === 'xyz');