Are there global functions in javascript?

There are global functions in JS, including: decodeURI(), escape(), eval(), isFinite(), isNaN(), Number(), parseFloat(), parseInt(), String() , unescape() and so on.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

JavaScript Global Function

decodeURI() function

decodeURI() function can decode the URI encoded by the encodeURI() function.

Syntax: decodeURI(uri)

• uri: required. A string containing the URI to decode or other text to decode.

decodeURIComponent() function

decodeURIComponent() function can decode the URI encoded by the encodeURIComponent() function.

Syntax: decodeURIComponent(uri)

encodeURI() function

encodeURI() function can use strings as URIs Encode.

The encodeURI() function will not escape the following ASCII punctuation symbols that have special meanings in URIs: , / ? : @ & = $ # (You can use the encodeURIComponent() method to separately The meaning of ASCII punctuation is encoded.).

Syntax: encodeURI(uri)

encodeURIComponent() function

The encodeURIComponent() function encodes a string as a URI component.

This method does not encode ASCII letters and numbers, nor does it encode these ASCII punctuation characters: - _ . ! ~ * ' ( ) .

Other characters (such as :;/?:@&= $,# these punctuation marks used to separate URI components) are replaced by one or more hexadecimal escape sequences.

Syntax: encodeURIComponent(uri)

escape() function

escape() function can encode strings , so that the string can be read on all computers.

This method does not encode ASCII letters and numbers, nor does it encode the following ASCII punctuation characters: * @ - _ . / . All other characters will be replaced by escape sequences.

Syntax: escape(string)

• string: required. The string to be escaped or encoded.

eval() function

eval() function evaluates a JavaScript string and executes it as script code.

If the parameter is an expression, the eval() function will execute the expression. If the argument is a Javascript statement, eval() will execute the Javascript statement.

Syntax: eval(string)

isFinite() function

isFinite() function is used to check whether its parameters It is infinity, which can also be understood as whether it is a finite number.

Syntax: isFinite(value)

• value: required. The number to detect.

Return value: If the parameter is NaN, positive infinity or negative infinity, false will be returned, otherwise true will be returned.

isNaN() function

isNaN() function is used to check whether its argument is a non-numeric value.

Syntax: isNaN(value)

If the parameter value is NaN or a non-numeric value such as string, object, undefined, etc., it returns true, otherwise it returns false.

Number() function

Number() function converts the value of an object into a number.

Syntax: Number(object)

If the value of the object cannot be converted to a number, the Number() function returns NaN.

parseFloat() function

The parseFloat() function parses a string and returns a floating point number.

This function specifies whether the first character in the string is a number. If it is, the string is parsed until it reaches the end of the number, and the number is returned as a number rather than as a string.

Syntax: parseFloat(string)

parseInt() function

parseInt() function can parse a string, and returns an integer.

Syntax: parseInt(string, radix)

When the value of parameter radix is ​​0, or the parameter is not set, parseInt() will judge the number based on string of base.

When the parameter radix is ​​omitted, JavaScript defaults to the radix of numbers as follows:

• If the string starts with "0x", parseInt() will parse the rest of the string into ten Hexadecimal integer.

• If string starts with 0, then ECMAScript v3 allows an implementation of parseInt() to parse the following characters as octal or hexadecimal digits.

• If string starts with a number from 1 to 9, parseInt() will parse it into a decimal integer.

String() function

String() function converts the value of an object into a string.

Syntax: String(object)

unescape() function

unescape() function can be passed escape() The encoded string is decoded.

Syntax: unescape(string)

Note: unescape() cannot be used to decode URI (UniformResourceIdentifier, referred to as "URI") . To decode a URI please use the decodeURI() method.

[Recommended learning: javascript advanced tutorial]

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