9 Pitfalls of JavaScript and analysis of _javascript techniques

1. Last comma

As with this code, note the last comma, which should be a good linguistic point (as Python's Dictionary of Data Type Dictionary allows). IE will report grammatical errors, but vague, you can only employ eyes from thousands of lines of code scan.

<script>
var theobj = {
City: "Boston",
State: "MA",
}
</script>
2. This reference will change

such as this code:

<input type= "button" value= "gotcha!" id= "MyButton" >
<script>
var MyObject = function () {
This.alertmessage = "Javascript rules";
This. ClickHandler = function () {
alert (this.alertmessage);
}
}();
document.getElementById ("TheText"). onclick = Myobject.clickhandler
</script>
Not as you would like, the answer is not "JavaScript rules." When the Myobject.clickhandler is executed, the red line in the code, where the reference to this actually points to a reference to document.getElementById ("TheText"). Can solve this:

<input type= "button" value= "gotcha!" id= "TheText" >
<script>
var MyObject = function () {
var self = this;
This.alertmessage = "Javascript rules";
This. OnClick = function () {
alert (Self.value);
}
}();
document.getElementById ("TheText"). onclick = Myobject.onclick
</script>
Essentially, that's the problem with JavaScript scopes. If you've seen it, you'll find more than one solution.

3. Identification of thieves

Do not use the same variable names as HTML IDs in JavaScript. The following code:

<input type= "button" id= "Thebutton" >
<script>
Thebutton = Get ("Thebutton");
</script>
IE will report an undefined error to the object. I can only say: IE sucks.

4. String only replaces first match

The following code:

<script>
var fileName = "This is a title". Replace ("", "_");
</script>
In fact, the result is "this_is a title". In JavaScript, the first argument for String.Replace should be a regular expression. So the right thing to do is to:

var fileName = "This is a title". Replace (//g, "_");