Javascript basic tutorial - for loop_basic knowledge

Using a loop is convenient if you want to run the same code over and over again, with different values ​​each time.

Copy code The code is as follows:

document.write(cars[0] "
");
document.write(cars[1] "
");
document.write(cars[2] "
");
document.write(cars[3] "
");
document.write(cars[4] "
");
document.write(cars[5] "
");

But let’s write it like this

Copy code The code is as follows:

for (var i=0; i {
document.write(cars[i] "
");
}

Example: Output numbers from 1-100

Copy code The code is as follows:

for(var i=0;i <=100;i )
{
document.write(i "
")
}

for is a pre-test loop, and can initialize variables before the loop and define the code to be executed after the loop. Its syntax is as follows

for(inintialization;expression;psot=loop-expression)statement

The execution process is as follows:

1. Execute initialization statement

2. Determine whether expression is true. If so, continue, otherwise terminate the entire loop.

3. Execute the statement code of the loop body

4. Execute post-loop-expression code

5. Return to step 2

The most commonly used form of for loop is for(var i=0; i

It means that the loop is executed a total of n times, which is very suitable for operations with a known number of loops.

Copy code The code is as follows:

var aNumbers = new Array();
var sMessage = "You entered:n";
var iTotal = 0;
var vUserInput;
var iArrayIndex = 0;
do{
vUserInput = prompt("Enter a number, or exit with '0'","0");
aNumbers[iArrayIndex] = vUserInput;
iArrayIndex ;
iTotal = Number(vUserInput);
sMessage = vUserInput "n";
}while(vUserInput != 0) //Exit the loop body when the input is 0 (default value)
sMessage = "Total:" iTotal;
Document.getElementById("xxx").innerHTML=sMessage;

The above is all about the for loop in JavaScript. I hope you guys like it.