JavaScript Beginner Question (Loops)
Today is my first day in JavaScript. The开发者_如何学Python book (JavaScript Definitive Guide) has an excersice printing all the factorials.
This is what I did:
<html>
<b><head> Factorial - JavaScript - Ex1</head></b>
<body>
<h2> Factorials List </h2>
<script>
var fact = 1;
var num = 1;
for(num <= 10; num++)
{
fact=fact*num;
document.write(num + "! = " + fact + "<br>");
}
</script>
</body>
</html>
There is a problem which I don't exactly know. I checked the book and the way that writer solved it was by initializing the variable num inside the loop FOR. I did that and it worked. But what is the difference between that and mine?
Enlighten me Experts :)
A for loop's syntax must be
for (<initializer>; <condition>; <increment>) {
<body>
}
While any of <initializer>, <condition> and <increment> can be omitted, none of the semicolons ; can be removed. That means, your for loop must be written with an extra semicolon:
var num = 1;
for(; num <= 10; num++)
// ^
Or just move the var num = 1; into the for, which is normally what people would do:
for (var num = 1; num <= 10; num ++)
// ^^^^^^^^^^^^
加载中,请稍侯......
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