JavaScript | While Loop
While Loop: A while loop is a control flow statement that allows code to be executed repeatedly based on the given Boolean condition. The while loop can be thought of as a repeating if statement.
Syntax:
while (condition) {
// Statements
}
Example: This example illustrates the use of while loop.
<!DOCTYPE html> <html> <head> <title> JavaScript While loop </title> </head> <body style="text-align:center;"> <div> <h1>GeeksForGeeks</h1> <h2>JavaScript While Loop</h2> </div> <p id="GFG"></p> <!-- Script to use while loop --> <script> var print = ""; var val = 1; while (val < 6) { print += "Geeks " + val; print+="<br>" val+=1; } document.getElementById("GFG").innerHTML = print; </script> </body> </html> |
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Output:
Do-While loop: A do-while loop is a control flow statement that executes a block of code at least once, and then repeatedly executes the block or not depending on a given boolean condition at the end of the block.
Syntax:
do {
// Statements
}
while (condition);
Example: This example illustrates the use of do-while loop.
<!DOCTYPE html> <html> <head> <title> JavaScript While loop </title> </head> <body style="text-align:center;"> <div> <h1>GeeksForGeeks</h1> <h2>JavaScript While Loop</h2> </div> <p id="GFG"></p> <!-- Script to use do-while loop --> <script> var print = "" var val = 0; do { print += "Geeks " + val; print +="<br>"; val+=1; } while (val < 6); document.getElementById("GFG").innerHTML = print; </script> </body> </html> |
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Output:
Comparison between while and do-while loop: The do-while loop executes the content of the loop once before checking the condition of the while loop. While the while loop will check the condition first before executing the content.
| While Loop | Do-While Loop |
|---|---|
| It is an entry condition looping structure. | It is an exit condition looping structure. |
| The number of iterations depends on the condition mentioned in the while block. | Irrespective of the condition mentioned in the do-while block, there will a minimum of 1 iteration. |
| The block control condition is available at the starting point of the loop. | The block control condition is available at the end point of the loop. |
Example: This example illustrates both while and do-while loop.
<!DOCTYPE html> <html> <head> <title> JavaScript loop </title> </head> <body style="text-align:center;"> <div> <h1 style="color:green;"> GeeksForGeeks </h1> <h2>JavaScript Loop</h2> </div> <h3>While Loop</h3> <p id="GFG"></p> <!-- Script to use while loop --> <script> var text = ""; var i = 1; while (i < 6) { text += "Geeks " + i+"<br>"; i++; } document.getElementById("GFG").innerHTML = text; </script> <h3>Do While Loop</h3> <p id="GFG1"></p> <!-- Script to use do-while loop --> <script> var text = "" var i = 1; do { text += "Geeks " + i+"<br>"; i++; } while (i < 6); document.getElementById("GFG1").innerHTML = text; </script> </body> </html> |
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