Detailed explanation of using template strings in ES6

This time I will bring you a detailed explanation of the use of template string in ES6. What are the precautions when using template string in ES6. The following is a practical case. Let’s take a look. take a look.

Write in front

Regarding ES6, it was finally released on July 18, 2015 The dust has settled. Although major browsers do not yet have full support, this does not prevent us from wanting to give it a try. On the backend, you can use Node.js(0.12) or For io.js and the front end, you can also use Babel or Traceur to pre-escape the syntax to ES5.

Regarding this series (I don’t know if it can become a series, I am always lazy), I will randomly select some content to learn. Everyone is welcome to actively correct errors and leave messages for discussion.

template strings

Usage

// 普通字符串
`In JavaScript '\n' is a line-feed.`
// 多行字符串
`In JavaScript this is
not legal.`
// 字符串中嵌入变量
var name = "Bob", time = "today";
`Hello ${name}, how are you ${time}?`  // Hello Bob, how are you today?

A new type of string literal syntax introduced in ES6 - template string. Technically explained, a template string is a string literal that embeds expressions within a string literal. To put it simply, it is a string with added variable function.

Let’s first look at our previous use of strings:

/**
 * Before ES6 字符串拼接
 */
var name = '丁香医生';
var desc = '丁香医生是面向大众的科普性健康类网站';
var html = function(name, desc){
  var tpl = '公司名：' + name + '\n'+
      '简介：'+ desc;
  return tpl;
}

And now:

var html = `公司名：${name}
  简介：${desc}`;

It's very simple.

Quote from MDN’s definition of template string:

Template strings use backticks () instead of double and single quotes in normal strings. Template strings can contain placeholders for specific syntax (${expression}). The expression in the placeholder is passed along with the surrounding text to a default function, which is responsible for connecting all the parts.

The placeholder ${} can be any js expression (function or operation), or even another template string, and its calculated result will be output as a string. If strings such as $ and { need to be used in the template, they need to be escaped.

Just look at an example to understand.

var x = 1;
var y = 2;
`${ x } + ${ y } = ${ x + y}` // "1 + 2 = 3"

Different from ordinary strings, template strings can also be written on multiple lines. All spaces, new lines, and indents in the template string will be output as is in the generated string.

However, simple template strings still have many limitations. like:

1. Special strings cannot be escaped automatically. (This can easily cause injection attacks)

2. Does not work well with internationalization libraries (i.e. does not format numbers, dates, text, etc. in specific languages)

3. There is no built-in loop syntax, (even conditional statements are not supported, only template nesting methods can be used)

# tagged template

To this end, the concept of label templates is introduced. The tag template introduces a tag before the backtick. This tag is a function that returns a value after a customized template string. Take the above example of the special character string.

/**
 * HTML 标签转义
 * @param {Array.<DOMString>} templateData 字符串类型的tokens
 * @param {...} ..vals 表达式占位符的运算结果tokens
 * 
 */
function SaferHTML(templateData) {
 var s = templateData[0];
 for (var i = 1; i < arguments.length; i++) {
  var arg = String(arguments[i]);
  // Escape special characters in the substitution.
  s += arg.replace(/&/g, "&")
      .replace(/</g, "<")
      .replace(/>/g, ">");
  // Don't escape special characters in the template.
  s += templateData[i];
 }
 return s;
}
// 调用
var html = SaferHTML`<p>这是关于字符串模板的介绍</p>`;

The label function receives multiple parameters.

1. The first parameter is an array containing string literals (that is, those values ​​without variable substitution)

2. The following parameters are the variable values ​​that have been replaced

Change example 1

var name = '丁香医生';
var desc = '丁香医生是面向大众的科普性健康类网站';
tag`公司名：${name}简介：${desc}`

The parameters of the tag are ['Company name:', 'Introduction:'], 'Doctor Lilac', 'Doctor Lilac is a popular science sexual health website for the public'.

With such methods, the power of control is greatly increased. Such as the internationalization library mentioned above and even loop statements.

Browser Compatibility

1. Server side, io.js supports

2. Browser side, FF34, chrome 41

3. Mobile terminal IOS 8, Android 4.4

4. IE Tech Preview

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

Recommended reading:

How to operate table in Bootstrap

js to realize conversion of milliseconds, days, hours, minutes and seconds

The above is the detailed content of Detailed explanation of using template strings in ES6. For more information, please follow other related articles on the PHP Chinese website!