Loops

for, do...while and while loop syntax is the same in JS as it is in Java.

let intArray = [1, 2, 3, 4];

// for loop
for (let i = 0; i < intArray.length; i++) {
  console.log("for loop: " + intArray[i]);
}

// while loop
let keepLooping = false;
while (keepLooping) {
  console.log("while loop, never executes");
}

// do...while loop
keepLooping = false;
do {
  console.log("do-while loop, executes at least once");
} while (keepLooping);

The for-of Loop

Similar to Java's enhanced for loop (for ( int num : arrayOfInts ) {}), JavaScript's for-of loop traverses the elements of an iterable collection - such as an array - placing each item in a variable.

// for-of loop
for (let num of intArray) {
  console.log("for-of loop: " + num);
}

• Unless your algorithm needs to use the index, this is the simplest way to iterate over an array.

The for-in loop

JavaScript's for-in loop traverses the indexes of a collection, placing each index in the loop variable.

// for-in loop
for (let i in intArray) {
  console.log("for-in loop: " + intArray[i]);
}

Skill++

To keep these two loops straight, remember:

• for-Of puts each Object in the variable.

• for-IN puts each INdex in the variable.

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