A relatively complete set of JavaScript interview questions (partial answers)

1. Multiple-choice questions

1. Which of the following statements will generate a runtime error: (a)

A.var obj = () ;//Syntax error

B.var obj = [];//Create array

C.var obj = {};//Create object

D.var obj = //;

Reason: var obj = new Array (); is correct; curly brackets in JavaScript represent creating objects. var obj = { id:1, name:"jacky" };alert(obj.name);The above example means creating an object with attribute id (value is 1) and attribute name (value is jacky). Attribute names can be enclosed in quotation marks to become "id", "name", or not quoted.

Of course, in addition to attributes, you can also create methods.

Test code

/* window.onload=function()
{
// var obj = ();
var obj1 = [];//object
var obj2 = {};//object
var obj3 = //;//undefine
alert(typeof(obj1));
alert(typeof(obj2));
alert(typeof(obj3));
}*/
function showName()
{
alert(this.name);
}
var obj = { id:1, name:"jacky", showName:showName };
obj.showName();

2. Which of the following words is not a javascript reserved word: (b)

A.with

B.parent

C.class

D.void

3. Please select the expression whose result is true: (c)

A.null instanceof Object (if(!(null instanceof Object)) is true)

B.null === undefined

C.null == undefined

D.NaN = = NaN

(1) null can indeed be understood as a primitive type, not as an Object!

null, int, float... and other types represented by keywords are not Object.

As for null as a parameter, it is just a special rule.

It can be understood this way:

The reference of the object represents a memory value. null is a null reference, which can be understood as the memory value is 0; according to this meaning, the code

(2) function f1(){

}

1. alert(f1 instanceof Function);//true

2. alert(f1 instanceof Object);/ /true

3. alert(Function instanceof Object);//true

4. alert(Object instanceof Function);//true

Function is an instance of Object, Object is an instance of Function

Function is the constructor of the function, and Object is also a function, and Function itself is also a function

Object.prototype is the apex of all prototype chains, instanceof will search the entire prototype chain

alert(Function);
alert(Function.prototype);
alert(Function.__proto__);
alert(Object);
alert(Object.prototype);
alert(Object.__proto__);
alert((function(){}).prototype);
alert((function(){}).__proto__);
alert((function(){}).__proto__.prototype);
alert((function(){}).prototype.__proto__);
alert(Array.__proto__);
alert((123).__proto__);
alert((Number).__proto__);
alert(("test").__proto__);
alert((String).__proto__);
alert((true).__proto__);
alert((Boolean).__proto__);
/* window.onload=function()
{
if(NaN == NaN)
{
alert("ddd");
}
}
*/

2. Indefinite multiple-choice questions

4. Please choose the one with a wrong understanding of javascript: (abcd)

A.JScript is the abbreviation of javascript

B.javascript is a Java script language developed by Netscape. Its purpose is to simplify the development of Java

C. The main reason why FireFox and IE have a lot of compatibility problems is that they have The support of javascript varies

D.AJAX technology must use javascript technology

5. The foo object has the att attribute, so to get the value of the att attribute, which of the following methods are acceptable: ()

A.foo.att

B.foo("att")

C.foo["att"]

D.foo{" att”}

E.foo[“a” ”t” ”t”]

6. Which HTML tags can be used to manually enter text without specifying special attributes: (ace)

7. Which of the following are global functions of javascript: (abc)

A.escape

B.parseFloat

C.eval

D.setTimeout

E.alert

8. The correct expressions about IFrame are: (abcd)

A. Through IFrame, web pages can embed the content of other web pages and dynamically change

B. Under the same domain name, the embedded IFrame can obtain the object of the outer web page

C. Under the same domain name Under the domain name, the outer webpage script can obtain the objects in the IFrame webpage

D. The size of the IFrame can be adjusted through the script

9. The correct expressions about the table are: (abcde)

A. The table can contain TBODY elements

B. The table can contain CAPTION elements

C. The table can contain multiple TBODY elements

D. Table The table can contain the COLGROUP element

E. The table can contain the COL element

10. The correct expressions about IE’s window object are: (acd)

A.window. The opener attribute itself points to the window object

The B.window.reload() method can be used to refresh the current page

C.window.location=”a.html” and window.location.href The function of =”a.html” is to replace the current page with the a.html page

D. The global variable g is defined; the variable can be accessed using window.g

3. Questions and answers:

1. Talk about the use of javascript array sorting method sort(), focusing on the use of sort() parameters and its internal mechanism

The implementation of sort has similar functions JAVA's comparator, data sorting starts from the first dimension of the multi-dimensional array

You can define your own sorting method, there are very few functions

2. Briefly describe the difference between DIV elements and SPAN elements .

DIV has a carriage return, but SPAN does not.

3. Combined with the text structure, let’s talk about the differences between innerHTML, outerHTML and innerText.

You only need to write this question to see clearly

The HTML in the innerHTML object, outerHTML includes the object and the text inside the

innerText object

4. Say a few XHTML specification contents (at least 3)

attributes in quotation marks, no unmatched tags, add definitions

5. Standardize the Web (or reconstruct the website) What relevant knowledge do you know? Briefly describe a few Web standards you know?

Web pages are mainly composed of three parts: Structure, Presentation and Behavior. The corresponding website standards are also divided into three aspects: structured standard language, mainly including XHTML and XML; performance standard language mainly including CSS; behavioral standards mainly include object model (such as W3C DOM), ECMAScript, etc.

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