Tips for bugs in JavaScript programming _ javascript skills

This article mainly introduces a few tips on how to easily introduce bugs in JavaScript programming. This article summarizes eight tips. if you cannot understand these tips, it will cause you a BUG in programming, if you need it, you can refer to JavaScript, which is one of the most popular programming languages today, but it is also a side effect of the features of the language. no matter how wonderful the language is, every day, thousands of programmers make a bunch of bugs. Do not laugh at others first. maybe you are one of them.

Here is an example of a few simple and fully valid JS snippets (you can test it on your console ):

The code is as follows:

Typeof NaN = 'number' // true

Infinity === 1/0 // true

0.1 + 0.2 = 0.3 // false, the same is true with parentheses.

"3" + 1 // '31'
"3"-1 // 2

Do you still trust your JavaScript?

1. minimum JS value

The code is as follows:

Number. MIN_VALUE> 0; // true

Number. MIN_VALUE is the minimum value that can be expressed in JavaScript, which is 5e-324. However, it is the Number closest to 0 in JS.

2. string connection

The code is as follows:

("Foo" ++ "bar") = "fooNaN" // true
"Why I am" + typeof + "" // why I am number

Parse JS to "foo" + (+ "bar"), which converts "bar" into a number.

3. parseInt function

The code is as follows:

ParseInt ('06'); // 6
ParseInt ('08'); // 0 note that the new version of Google has been fixed
ParseInt (null, 24) === 23 // true

4. is null an object?

The code is as follows:

Typeof null // object
Null instanceof Object // false

5. return returned content

The code is as follows:

Function myjson ()
{
Return
[
2
]
}

Myjson (); // undefined

The content returned by return must be in the same line as return.

6. strange numbers

The code is as follows:

012 = 12 // false
'012' = 12 // true
"3" + 1 // '31'
"3"-1 // 2
0.1 + 0.2 = 0.3 // false
0.1 + 0.7 = 0.8 // false
0.2 + 0.7 = 0.9 // false
9999999999999999 // 10000000000000000
9999999999999999-1 // 10000000000000000
111111111111111111111 // 111111111111111110000

7. weird parameters

The code is as follows:

Function hello (what ){
Alert (arguments [0]); // vicky
What = "world ";
Return "Hello," + arguments [0] + "! ";
}

Hello ("vicky"); // "Hello, world! "

8. a big equal sign

The code is as follows:

NaN = NaN; // false
[] = False; // true
"" = False; // true
Null = false; // false
[] =! [] // True

Window. window = window // true
Window. window === window // false, some browsers are true
Window = document // true, some browsers are false

("0" & {}) = 0 // false
(0 & {}) = 0 // true
0 = "0" // true
[] = 0 // true