1. Error situation: Syntax error
<div id=div1></div>
<script language="javascript">
("never-online";
</script>
Explanation: The above example is a typical example. The method names must be enclosed with () and the parameters in () are included.
Maybe someone disdained it, but in the forum. There are many such mistakes.
Tips: This kind of problem is relatively simple to solve and can generally be solved.
2. Error situation: Incorrect usage of quotes
<script>
s="alert("never-online")";
</script>
Explanation: In JavaScript or vbscript programming, the probability of quotation marks errors is high. No matter how rich programming experience is, encountering a large number of string splicing, or accidentally typing the error ("), there will be "grammatical errors" or "missing".
Tips: When splicing a large number of characters, you need to pay attention to the escape usage of quotes. As above, you can write it as: s="alert(\"never-online\")"; or s='alert("never-online")';
Related links: js skills--the wonderful use of escape character "\"-/bluedestiny/archive/2006/03/15/
3. Error situation: Unknown soft error
<script language="javascript">
cntMax=100;
div=("DIV");
(div);
var myFun=function() {
for(var i=0;i<cntMax;i++);
+="<b>i: " +i+ "</b><br/>";
+="";
}
myFun();
</script>
When it runs, there is no prompt for an error, which gives people the illusion that soft errors like this are more difficult to find.
Therefore, you must be careful when writing programs in daily life.
Tips: You should pay attention to your habits when programming, such as in for(var i=0;i<cntMax;i++); here, if the semicolon is used to enclose it with {, this situation can be completely avoided. When reading the SDK document, you should read it carefully. Case errors generally occur with prompts such as "the object does not have this method", but in the script, the object can dynamically add methods and attributes. So, there will be no errors in the above="". And the innerHTML of the div does not get the value.
4. Error situation: Error in understanding the language
The most common one may be considered this keyword, here is an example to illustrate
This semantics: a pointer to the current object.
example:
<script>
function a() {
= "never-online";
= function() {
alert();
}
}
var b = new a();
();
</script>
I believe that many people understand the above example. This points to a()
Let’s take a look at the following example:
<div id=div1>div container - onmouseover handle</div>
<script>
function a() {
= val = 'never-online';
var div = ("div1");
=function() {
alert();
}
alert();
}
a();
</script>
Some brothers may not understand this example. After taking a closer look, you can also predict the output results.
Explanation: = val = 'never-online' is an assignment, and this in it points to the current object a();
The object in this refers to the object ("div1"), (because div does not belong to the a object), that is, it is equivalent to writing the code here:
<div id=div1 onmouseover="alert()">div container - onmouseover handle</div>
Therefore, it is not surprising that undefined appears in the function.
<div id=div1></div>
<script language="javascript">
("never-online";
</script>
Explanation: The above example is a typical example. The method names must be enclosed with () and the parameters in () are included.
Maybe someone disdained it, but in the forum. There are many such mistakes.
Tips: This kind of problem is relatively simple to solve and can generally be solved.
2. Error situation: Incorrect usage of quotes
<script>
s="alert("never-online")";
</script>
Explanation: In JavaScript or vbscript programming, the probability of quotation marks errors is high. No matter how rich programming experience is, encountering a large number of string splicing, or accidentally typing the error ("), there will be "grammatical errors" or "missing".
Tips: When splicing a large number of characters, you need to pay attention to the escape usage of quotes. As above, you can write it as: s="alert(\"never-online\")"; or s='alert("never-online")';
Related links: js skills--the wonderful use of escape character "\"-/bluedestiny/archive/2006/03/15/
3. Error situation: Unknown soft error
<script language="javascript">
cntMax=100;
div=("DIV");
(div);
var myFun=function() {
for(var i=0;i<cntMax;i++);
+="<b>i: " +i+ "</b><br/>";
+="";
}
myFun();
</script>
When it runs, there is no prompt for an error, which gives people the illusion that soft errors like this are more difficult to find.
Therefore, you must be careful when writing programs in daily life.
Tips: You should pay attention to your habits when programming, such as in for(var i=0;i<cntMax;i++); here, if the semicolon is used to enclose it with {, this situation can be completely avoided. When reading the SDK document, you should read it carefully. Case errors generally occur with prompts such as "the object does not have this method", but in the script, the object can dynamically add methods and attributes. So, there will be no errors in the above="". And the innerHTML of the div does not get the value.
4. Error situation: Error in understanding the language
The most common one may be considered this keyword, here is an example to illustrate
This semantics: a pointer to the current object.
example:
<script>
function a() {
= "never-online";
= function() {
alert();
}
}
var b = new a();
();
</script>
I believe that many people understand the above example. This points to a()
Let’s take a look at the following example:
<div id=div1>div container - onmouseover handle</div>
<script>
function a() {
= val = 'never-online';
var div = ("div1");
=function() {
alert();
}
alert();
}
a();
</script>
Some brothers may not understand this example. After taking a closer look, you can also predict the output results.
Explanation: = val = 'never-online' is an assignment, and this in it points to the current object a();
The object in this refers to the object ("div1"), (because div does not belong to the a object), that is, it is equivalent to writing the code here:
<div id=div1 onmouseover="alert()">div container - onmouseover handle</div>
Therefore, it is not surprising that undefined appears in the function.