JavaScript face question Encyclopedia (recommended) _javascript tips

Source: Internet
Author: User
Tags object model

1. What is the value of Y and Z?

<script type= "Text/javascript" >
var x = 1;
var y = 0;
var z = 0;
function Add (n) {n=n+1;}
y = Add (x);
function Add (n) {n=n+3;}
z = Add (x);
</script>

are undefined because there is no return value.

2.javascript is object-oriented, how to embody the JavaScript inheritance relationship?

Use prototype to implement.

3.javascript How to select a checkbox, how to set it invalid?

Document.all.cb1[0].disabled = true;

4.form input can be set to ReadOnly and disable, ask 2 What is the difference?

ReadOnly is not editable, but can be selected and copied; values can be passed to the background

Disabled cannot be edited, cannot be copied, cannot be selected, values cannot be passed to the background

What are the commands for 3 pop-up message Reminders (Warning window, confirmation window, information Input window) in 5.js?

Alert
Confirm
Prompt

What types of input are in 6.form?

What is the difference between the 2 variable ranges of 7.javaScript?

Global variables: Valid on current page

Local variables: Valid within method

8. Enumerate the 3 main data types of JavaScript, 2 types of composite data and 2 special data types.

Primary data type: String, Boolean, number

Composite data type: function, Object

9. How do you catch exceptions in your program?

Window.error

Try{}catch () {}finally{}

10. Write out the return result of function Datedemo, the system time is assumed to be today

function Datedemo () {
var d, s= "Today's date is:";
D = new Date ();
S + + d.getmonth () + "/";
S + + d.getdate () + "/";
S + + d.getyear ();
return s;
}

Result: Today's date is: 7/17/2010

11. Write out the results of the program running?

For (i=0, j=0; i<10, j<6; i++, J + +) {
k = i + j;
}

Results: 10 (Beware of traps)

12. The results of the operation?

function Hi () {
var A;
alert (a);
}

Result: undefined

13. The results of the operation?

function Hi () {
var a = null;
alert (a);
}

Result: null

14. The object model of the browser?

Window

Top-level objects

Window.alert (msg)

Window.prompt ()

Window.confirm ()

if (Window.confirm ()) {
...
}

window.open ()

Window.close ()

Document

document.write ()

History

When a user browses to a Web page, the browser saves a list of URLs for the most recently visited Web page. This list is represented by a History object.

History.back (): Back

History.forward (): Forward

History.go (n): Positive number indicates forward, negative number indicates backward

Location

Represents the URL information for a window or frame that is currently open.

Location.href: redirect

Equivalent to Location.assign (URL)

Location.host: Similar to www.163.com:80

Navigator

Represents the browser's information and JS operating environment

Navigator.cookieenabled: This property indicates whether cookies are enabled

Screen

The size and color of the monitor used to display the Web page

Screen.width/screen.height: Indicates the resolution of the display (total width, height)

What is the 15.XMLHTTPRequest object?

Ajax Principles

16. The optional value of the attribute target for the hyperlink: What is the difference between _blank, _parent, _self, _top, and frame names?

What are the 17.javascript common objects?

String, Math, date, and array objects

18.innerhtml,innertext,outerhtml,innertext the difference?

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