# Manipulation of Strings and Numbers in Javascript

• 2021-07-13 04:05:47
• OfStack

1. `length ` Returns the length of a string

``````
' abcd'.length; //4 ``````

2. `Math.ceil(num) ` Rounding up, no matter what is after the decimal point, even if. 00001, it will go up by one place.

``````
Math.ceil(25.9); //26
Math.ceil(25.5); //26
Math.ceil(25.1); //26 ``````

3. `Math.floor(num)` Rounding down, no matter what is after the decimal point, even if it is. 99999, it will be subtracted by one place.

``````
Math.floor(25.9); //25
Math.floor(25.5); //25
Math.floor(25.1); //25 ``````

4. `Math.round(num)` 4 houses and 5 entrances.

``````
Math.round(25.9); //26
Math.round(25.5); //26
Math.round(25.1); //25 ``````

5. `Math.abs(num)` Returns the absolute value of the number.

``````
Math.abs(-10); // 10
Math.abs(10); // 10
Math.abs(-10.5); // 10.5 ``````

6. `Math.max(n,n1,n2)` Returns the largest of the specified numbers [until ECMASCript v3, this method has only two parameters].

``````
Math.max(1,32,4,5,6,7,87) //87 ``````

7. `Math.min(n,n1,n2) ` Returns the smallest of the specified numbers [until ECMASCript v3, this method has only two parameters].

``````
Math.max(1,32,4,5,6,7,87) //1 ``````

8. `Math.random() ` Random number, such as returning a random number between specified numbers, the formula is: `Math.random()*(y-x) + x`

``````
// Return 0-1 The random number between, with decimal by default
Math.random();
// Only return below 0 And 1 Random numbers, remember yes and no 0 Is 1
Math.round( Math.random() )
//5-10 Random number of
Math.round( Math.random()*5 + 5 )
//10-20 Random number of
Math.round( Math.random()*10 + 10 )
//0-100 Random number of
Math.round( Math.random()*100 ) ``````

Math there are many methods, other not commonly used, here will not be introduced, the specific can see this article.

9. `charAt() ` Returns the character at the specified position.

``````
' abcd'.charAt(0); //a
' abcd'.charAt(1); //b
' abcd'.charAt(2); //c ``````

10, `Math.ceil(num) `0 Gets the encoding of the character at the specified position ( `unicodo` Coding).

``````
' abcd'.charCodeAt(1) //98
' abcd'.charCodeAt(2) //99 ``````

11, `fromCharCode()` One or more of the specified `Unicode ` Value, and then returns a string.

``````
Math.ceil(25.9); //26
Math.ceil(25.5); //26
Math.ceil(25.1); //26 ``````
0

12, `indexOf() ` Returns the index that occurs at the first place of a substring in a string. Returns-1 if there is no match.

``````
Math.ceil(25.9); //26
Math.ceil(25.5); //26
Math.ceil(25.1); //26 ``````
1

13. `substring() ` If it is 1 parameter, the subscript is returned from the `start` Characters from beginning to end at; If it is two parameters, the extract string is derived from the `start` To `end-1` The character between.

``````
Math.ceil(25.9); //26
Math.ceil(25.5); //26
Math.ceil(25.1); //26 ``````
2

14, `substr() ` If it is 1 parameter, the subscript is returned from the `start` Characters from beginning to end at; If it is two parameters, the extract string is derived from the `start` Position start interception `end` Bit.

``````
' abcd'.substr(3) //d
' abcd'.substr(0,2) //ab
' abcd'.substr(1,2) //bc ``````

15, `slice() ` If it is 1 parameter, the subscript is returned from the `start` The characters from the beginning to the end, if it is a negative number, take several characters from the back; If it is two parameters, the extract string is derived from the `start` To `end-1` If the first one is negative, then the second one cannot be less than the position of the first character, and this comparison wraps around.

See the following code for details.

``````
Math.ceil(25.9); //26
Math.ceil(25.5); //26
Math.ceil(25.1); //26 ``````
4

16, `replace() ` String replacement.

``````
Math.ceil(25.9); //26
Math.ceil(25.5); //26
Math.ceil(25.1); //26 ``````
5

17, `split() ` Strings are divided into arrays. If there is one parameter, it is divided according to the parameter, and if there are two, it is divided according to the second parameter

``````
Math.ceil(25.9); //26
Math.ceil(25.5); //26
Math.ceil(25.1); //26 ``````
6

18, `toUpperCase() ` Convert lowercase strings to uppercase

``````
Math.ceil(25.9); //26
Math.ceil(25.5); //26
Math.ceil(25.1); //26 ``````
7

19, `toUpperCase() ` Convert uppercase strings to lowercase

``````
' ABCD'.toUpperCase( " ); //abcd ``````

20, `Math.round(num)`1 The string is converted to a number, and stops when it encounters a non-number. The first character cannot be converted to a number, and returns `Math.round(num)`2

``````
Math.ceil(25.9); //26
Math.ceil(25.5); //26
Math.ceil(25.1); //26 ``````
9

21, `parseFloat()` The string is converted to a decimal, and stops when it encounters a non-number. The first character cannot be converted to a number, and returns `Math.round(num)`2

``````
parseInt('10') //10
parseInt('10abc') //10
parseInt( ' 10.256 ' ) //10.256
parseInt( ' 10.25W6 ' ) //10.25
parseInt( ' W60 ' ) //NaN ``````

Summarize

The above is about js string and the number of the operation method of the whole content, I hope that the content of this article to everyone's study or work can bring 1 set of help, if you have any questions, you can leave a message to communicate.

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