For loop statements in Javascript

Using for statements

The ordinary for loop statement

  • A for loop statement has the form:
    for(initialize ; expression ; increment) {
  • A for loop combines the three steps of initializing, testing, and incrementing into one statement:
    <script type="text/javascript">
      var count = 0;             // initialize the condition
      // The initializing part is: count = 0  (when the loop starts)
      // The test part is     : count < 5 (if true ; execute the body statements)
      // The incrementing part is: count++  (executes for each loop)
      for (count = 0; count < 5; count++) {
        document.write("I got a hotdog !<br>");
      document.write("At end Count: "+count+"<br>");

The EMPTY for loop statement

  • You can have NO Statement in a for Loop, but the use of it is rare:
    <script type="text/javascript">
      for (var count = 0; count<5;
         document.write("count: "+ count++ +"<br>"));
      // There is no statement in the body of the for loop
      ; // This is an empty statement

The enhanced for loop statement

  • A enhanced for loop (or for/in loop) statement has the form:
    for (variable in object) {
  • The for/in statement provides a way to loop through the properties of an object.
  • The body of the for/in loop is executed once for each property of object.
  • Before the body of the loop is executed, the name of one of the object's properties is assigned to variable.
    <script type="text/javascript">
      var verbs = ["composite ", "a ", "This ",
        "using ", "index!", "is ",
        "indirect ", "string "];
      var index = [2, 5, 1, 0, 7, 3, 6, 4];
    // verbs and index are arrays, which
    // both are a kind of an object in Javascript
      for (var i in index) {

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