The dowhile Loop | Inside JavaScript

The do while Loop

The do while loop executes its statements until a test condition evaluates to false. Unlike a while loop, the statements in the body of the do while loop are executed at least once. Here's the syntax of this loop:

 do  statements  while (condition)

The following parts comprise this loop:

statements . The body of the loop, a set of statements that are executed at least once, and executed again each time the condition evaluates to true.
condition . Evaluated after each pass through the loop. If condition evaluates to true, the statements in the loop's body are executed again. When condition evaluates to false, the loop terminates.

The do while loop was new in version 4.0 of the Netscape Navigator and Internet Explorer, as you see in Table 3.4.

Table 3.4. The do while Loop

Statement	NS2	NS3	NS4	NS6	IE3a	IE3b	IE4	IE5	IE5.5	IE6
`do while`			x	x			x	x	x	x

Here's how we can search for "Claire" in an array, just as we did in the preceding example with a while loopbut this time, we're using a do while loop:

(Listing 03-05.html on the web site)

 <HTML>      <HEAD>          <TITLE>              Using the do...while Loop          </TITLE>      </HEAD>      <BODY>          <H1>Using the do...while Loop</H1>          <SCRIPT LANGUAGE="JavaScript">              <!--  var index = 0, data = new Array(5)   data[0] = "Fank"   data[1] = "Tom"   data[2] = "Claire"   data[3] = "Sara"   data[4] = "Jane"   do{   index++   }while(data[index] != "Claire")   alert("Found Claire at index " + index)  // -->          </SCRIPT>      </BODY>  </HTML>