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This article mainly introduces what the template string is in JS ES, it has certain reference value, interested friends can refer to it, I hope you can learn a lot after reading this article, let's take you to know it.

1. What is the template string?

The template string (Template String) is an enhanced version of the string that uses backquotes (```) instead of double and single quotes in the bandpass string. It can be used as a normal string, to define a multiline string, or to embed variables in a string.

The common usage is as follows:

/ / the string wrapped with `symbol is called template string let str = `template str`console.log (typeof str, str); / / string this is str2. Multiline template string

The template string provided by ECMAScript 2015 is different from the normal string in that the spaces, indents, and newlines in the template string are preserved.

The sample code is indicated as follows:

Let str = `this is str`console.log (typeof str, str); / * template string with expression

The template string supports embedded expressions, and the syntax structure is as follows:

`$ {expression} `

The sample code is as follows:

Let str1 = `this is str1`let str2 = `this is str2` / / just write the expression into ${} let and = `$ {str1} and ${str2} `console.log (and); / / this is str1 and this is str23. Template string with label

The function of the template string is not just the above. It can be immediately followed by a function name that will be called to process the template string. This is called the tag template feature (tagged template).

Let str = 'str' console.log`this is ${str} `; / / equivalent to console.log ([' this is','], str)

A tag template is not a template, but a special form of function call. "tag" refers to a function, followed by a template string that is its parameter.

4. Original string

In the first parameter of the tag function, there is a special property, raw, that allows you to access the original string of the template string instead of the specially replaced character.

The sample code is as follows:

/ * the original string is applied in the labeled template string * there is a raw attribute in the first argument of the function, which gets the original string of the string. * the so-called original string refers to the content when the template string is defined, not the content after processing * / function tag (string) {console.log (string.raw [0]);} tag `string test line1\ n string test line2` / / string test line1\ n string test line2

In addition, using the String.raw () method to get out the function key original string is the same as the default template function and string concatenation creation.

The sample code is as follows:

Let str = String.raw `Hi\ n$ {2q3}! `; / /, the character after Hi is not a newline character,\ and n are two different characters console.log (str); / / Hi\ n5room5. Determine whether a string is included

5.1includes () method

The includes () method is used to determine whether a string is contained in another string and returns true or false based on the result of the judgment.

The syntax structure is as follows:

Str.includes (searchString [, position])

Parameter description:

SearchString: the string to search for in this string.

Position: (optional) from which index position of the current string to start searching for substrings. The default value is 0.

It is worth noting that the includes () method is case sensitive.

The sample code is as follows:

Let str = 'abcdef';console.log (str.includes (' c')); / / trueconsole.log (str.includes ('d')); / / trueconsole.log (str.includes ('z')); / / falseconsole.log (str.includes ('A')); / / false

The includes () method provided by ECMAScript 2015 is case-sensitive, and now we extend a case-insensitive

The sample code is as follows:

String.prototype.MyIncludes = function (searchStr, index = 0) {/ / change all the strings to be judged in lowercase let str = this.toLowerCase () / / change the incoming string to lowercase searchStr = searchStr.toLowerCase (); return str.includes (searchStr, index)} let str = 'abcdef';console.log (str.MyIncludes (' c')); / / trueconsole.log (str.MyIncludes ('d')) / / trueconsole.log (str.MyIncludes ('z')); / / falseconsole.log (str.MyIncludes ('A')); / / true5.2startsWith () method

The startsWith () method is used to determine whether the current string begins with another given substring and returns true or false based on the result of the judgment.

The syntax structure is as follows:

Str.startsWith (searchString [, position])

Parameter description:

SearchString: the string to search for in this string.

Position: (optional) from which index position of the current string to start searching for substrings. The default value is 0.

It is worth noting that the startsWith () method is case sensitive.

The sample code is as follows:

The let str = 'abcdef';/* * startsWith () method is used to determine whether the current string begins with another given substring and returns true or false based on the result of the judgment. The * str.startsWith (searchString [, position]) parameter indicates searchString: the string to be searched in this string. Position: (optional) from which index position of the current string to start searching for substrings. The default value is 0. ! It is worth noting that the startsWith () method is case sensitive. * / console.log (str.startsWith ('a')); / / trueconsole.log (str.startsWith ('c', 2)); / / trueconsole.log (str.startsWith ('c')); / / flase5.3endsWith () method

The endsWith () method is used to determine whether the current string "ends" with another given substring and returns true or false based on the result of the judgment.

The syntax structure is as follows:

Str.endsWith (searchString [, position])

Parameter description:

SearchString: the string to search for in this string.

Position: (optional) from which index position of the current string to start searching for substrings. The default value is 0.

It is worth noting that the endsWith () method is case sensitive.

The sample code is as follows:

Let str = 'abcdef';console.log (str.endsWith (' f')); / / trueconsole.log (str.endsWith ('c', 3)); / / trueconsole.log (str.endsWith ('c')); / / flase

The following two methods can extend a case-insensitive one by yourself.

Thank you for reading this article carefully. I hope the article "what is the template string in JS ES" shared by the editor will be helpful to you. At the same time, I also hope you will support us and follow the industry information channel. More related knowledge is waiting for you to learn!

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