array-iterating

"use strict";

const toMs = ( diff ) => {
	return diff[ 0 ] * 1000 + diff[ 1 ] / 1000;
};

const SIZE = 1000000;

let arr = [];
for ( var i = 0; i < SIZE; ++i ) {
	arr.push( Math.floor( Math.random() * 256 ) );
}

/////////////////// simple loop
let prev = process.hrtime();
let sum = 0;

for ( var i = 0; i < SIZE; ++i ) {
	sum += arr[ i ];
}

let t0 = toMs( process.hrtime( prev ) );

console.log( "Time cost of simple loop: ", t0, sum );

////////////////// for ... in
prev = process.hrtime()
sum = 0;
for ( var i in arr ) {
	sum += arr[ i ];
}

let t1 = toMs( process.hrtime( prev ) );

console.log( "Time cost of for ... in: ", t1, sum );
console.log( "ratio: ", t1 / t0 );

////////////////// for ... of
prev = process.hrtime()
sum = 0;
for ( var val of arr ) {
	sum += val;
}

let t2 = toMs( process.hrtime( prev ) );

console.log( "Time cost of for ... of: ", t2, sum );
console.log( "ratio: ", t2 / t0 );

/////////////////// forEach
prev = process.hrtime()
sum = 0;
arr.forEach( function ( val ) {
	sum += val;
} );

let t3 = toMs( process.hrtime( prev ) );

console.log( "Time cost of forEach: ", t3, sum );
console.log( "ratio: ", t3 / t0 );