Javascript BASICS (1), Javascript BASICS (

Javascript BASICS (1), Javascript BASICS (
My CSDN blog address: http://blog.csdn.net/caicongyang 1. Five primitive types of Javascript

Undefined, Null, String, Boolean, Number

The Undefined data type has only one value: undefined

Null data type has only one value: null

Values of the Boolean data type include true and false.

Demo:

  <script type="text/javascript">  alert(typeof s);//undefined    var falg = true;  alert(typeof falg);//boolean    var s1 ="hello";  alert(typeof s1);//string    var s3 = 3;  alert(typeof s3);//number    var s4 = null;  alert(s4);//null  var s2 = new String("hello");  alert(typeof s2); //object    alert(undefined == null);//true    </script>

2. Forced type conversion Boolean (value) Number (value) String (value)
3. Array

<Script type = "text/javascript"> // first definition method var arr1 = new Array (3); arr1 [0] = "apple "; arr1 [1] = "HTC"; arr1 [2] = "Haiwei"; alert (arr1.length); alert (arr1 [0]); alert (arr1.valueOf ()); // value: arr1.reverse (); // reverse order: alert (arr1.toString (); // value: arr1.push ("xiaomi"); // Add the element alert (arr1.toString ()); arr1.shift (); // Delete the first element of the array, alert (arr1.toString (); alert (arr1.pop ()); // Delete and return the last element of the Array // The second definition method var arr2 = new Array ("apple", "plum", "banana "); // method 3: var arr3 = ["headset", "Mobile Phone"]; </script>

My CSDN blog: http://blog.csdn.net/caicongyang

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