for loop in JavaScript is most often used to execute a block of code with different value each time. So, to reduce the code length instead of adding number of code lines using different value each time, for loop, is used to execute the single line multiple times.
Syntax
1 2 3 4 | for([variable-initialization]; [condition]; [final-expression]){ // statements to be executed here each time;} |
variable-initialization: the first expression to initialize the variable that is to be used as iteration counter.
condition: second expression that is to evaluated to decide whether to execute the next iteration of loop. If true, the loop is executed otherwise it terminates the loop.
final-expression: the last expression that is evaluated at the end of iteration. Generally it updates the counter variable.
statements: the code statements that are executed for each condition evaluated to true.
Example
1 2 3 4 | for(var i=1; i<=7; i++){ document.write('<font size=\"' + i + '\">Hello World</font><br />');} |
Above example shows the use of for loop in JavaScript by executing a single line of code how you can increase the size of font in each loop by incrementing the value of variable i.
