It contains some cases where a nice syntax is used in expense of performance

nice-syntax-bad-performance.js

'use strict';

var NUM_ITERATIONS = 99999999;
var i, tmp, tmp2, initTime, stopTime;

// Iteration using for loop assigning the value always
initTime = Date.now();
for (i = 0; i < NUM_ITERATIONS; i++) {
  tmp = (i % 2) || tmp;
}
stopTime = Date.now();

console.log('Iterate using for loop by assigning the value when have to change and not: %s ms', stopTime - initTime);

// Iterate using a if condition to check if the value have to change
initTime = Date.now();

for (i = 0; i < NUM_ITERATIONS; i++) {
  tmp2 = (i % 2);

  if (tmp2 !== 0) {
    tmp = tmp2;
  }
}

stopTime = Date.now();

console.log('Iterate using for loop by wrapping the value calculation in a boring if conditional: %s ms', stopTime - initTime);

function checkMod (value) {
  var tmp = (value % 2);

  if (tmp !== 0) {
    return tmp;
  } else {
    return value;
  }
}

initTime = Date.now();
for (i = 0; i < NUM_ITERATIONS; i++) {
  tmp = checkMod(i);
}
stopTime = Date.now();

console.log('Iterate using for loop by wrapping the value calculation in a function called for each iteration: %s ms', stopTime - initTime)

// Iterate using for loop by wrapping the value calcualtion in a function declared on each iteration
initTime = Date.now();
for (i = 0; i < NUM_ITERATIONS; i++) {
  tmp = (function (value) {
    var tmp = (value % 2);

    if (tmp !== 0) {
      return tmp;
    } else {
      return value;
    }
  }(i));
}
stopTime = Date.now();

console.log('Iterate using for loop by wrapping the value calculation in a function declared on each iteration: %s ms', stopTime - initTime);

// Using conditional if/else
initTime = Date.now();
for (i = 0; i < NUM_ITERATIONS; i++) {
  tmp = 0.5 - Math.random();
 
  if (tmp < 0) {
    tmp = 0;
  }
}
stopTime = Date.now();
 
console.log('Checking value and assigning one when a condition is not fulfilled: %s ms', stopTime - initTime);
 
// Using conditional Math.max()
initTime = Date.now();
for (i = 0; i < NUM_ITERATIONS; i++) {
  tmp = Math.max(0.5 - Math.random(), 0);
}
stopTime = Date.now();
 
console.log('Checking value and assigning one using Math.max: %s ms', stopTime - initTime);