What are For Loops And how do you use them in JavaScript?

The for statement creates a loop that consists of three optional expressions, enclosed in parentheses and separated by semicolons, followed by a statement or a set of statements executed in the loop.

The for loop has the following syntax:

for (<a href='http://forum.freecodecamp.com/t/javascript-while-loop/14668' target='_blank' rel='nofollow'>initialization]; [condition]; [final-expression]) {  
    code block to be executed                  
}

The [initialization] is executed before the loop (the code block) starts.

The [condition] defines the condition for running the loop (the code block).

The [final-expression] is executed each time after the loop (the code block) has been executed.

Example in JavaScript:

var ourArray = [];
for (var i = 0; i < 5; i++) {
    ourArray.push(i);
}

From the example above, you can read:

[initialization] sets a variable before the loop starts (var i = 0).

[condition] defines the condition for the loop to run (i must be less than 5).

[final-expression] increases a value (i++) each time the code block in the loop has been executed.

Why do we need “for loops”?

For loops are used to loop through a block of code for a known number of times. Sometimes only the computer knows how many times the loop will occur, not you, either way it is still known.

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