This article will show you what typescript is

One 、JavaScript The biggest problem

The most common types of errors written by programmers can be described as Type error ： A certain type of value is used where different types of values are expected . This may be due to a simple spelling mistake 、 Unable to understand the Library API The surface of the 、 Wrong assumptions about runtime behavior or other errors .

Use JavaScript The most prominent problem in writing code is type checking ： because JavaScript yes Weak type language , Most users can only use the code Operation phase To find the wrong type , This makes the error can not be found and repaired in time , It has buried hidden dangers for future development .

JavaScript No ability to express the relationship between different code units . combination JavaScript Quite strange Runtime semantics , This mismatch between language and program complexity makes JavaScript Development has become a difficult task to manage on a large scale .

TypeScript The goal is to be JavaScript programmatic Static type checker —— let me put it another way , Is a tool that runs before the code runs （ static state ） And make sure the type of program is correct （ Type checking ）, So that we can find the type error problem in time in the code writing stage .

Two 、 What is? TypeScript

TypeScript Is a free and open source programming language developed by Microsoft . It is JavaScript One of the Superset , And it essentially adds optional static typing and class-based object-oriented programming to the language .

TypeScript It's a very popular kind of JavaScript Language extension . It's in the existing JavaScript A type layer is added to the syntax , And even if this layer is deleted , It will not affect the original performance of the runtime . Many people think that TypeScript “ Just a compiler ”, But a better understanding is to put TypeScript As two separate systems ： compiler （ That is, the part dealing with grammar ） and Language tools （ That is, dealing with the part integrated with the editor ）.

3、 ... and 、JS , ES , TS The relationship between

• 1995 year ：JavaScript Be born

  Netscape at that time was relying on its Navigator Browser becomes Web The most famous first generation Internet company when the era opened .

  Because Netscape wants to be static HTML Add some dynamic effects to the page , therefore Brendan Eich It was designed in two weeks
  JavaScript Language .

  It's called JavaScript, The reason is that at that time Java Language is very popular , Just want to rub a wave of heat , actually JavaScript Except in grammar Java, The rest of it doesn't matter .

• 1997 year ：ECMAScript Be born

  Because Netscape was developed JavaScript, A year later, Microsoft imitated JavaScript Developed JScript, In order to make JavaScript Become a global standard , Several companies are united ECMA（European Computer Manufacturers Association）（ European Association of computer manufacturers ） The organization has developed JavaScript The standard of language , go by the name of ECMAScript standard .

• 2015 year ：TypeScript Be born

  TypeScript yes JavaScript Superset （ It will eventually be compiled as JavaScript Code ）, Which contains JavaScript All elements of , Can run JavaScript Code for , And expanded JavaScript The grammar of . Compared with JavaScript , It also adds static types 、 class 、 modular 、 Functions in interface and type annotation , Easier to develop large projects .

  TypeScript Provide up-to-date and evolving JavaScript characteristic , Including those from 2015 Year of ECMAScript And features in future proposals , For example, asynchronous function and Decorators, To help build robust components .

Sum up the relationship between the three in one sentence ：ECMAScript Standard language ,JavaScript yes ECMAScript The implementation of the ,TypeScript yes JavaScript Superset .

Four 、 Why use TypeScript

TypeScript Expanded JavaScript, Provide powerful Type checking and Grammar tip function , Combination such as VS code This kind of compiler , Can greatly improve the development efficiency , Reduce the maintenance cost in the later stage of the project ：