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 In the past, when we wanted to assign a value to a variable, such as an array type and an object type, to assign a value to a variable, we could only specify the value directly. It is very troublesome to write in this way, but under the ES6 syntax specification, it is allowed to directly extract the required values from arrays and objects according to a certain pattern, and directly assign variables to variables. This method is called Destructuring, which is simple to understand. That is, the left and right sides of the equal sign are equal.

In JS, pseudo-arrays are very common, also called array-like. So it is very important to understand and understand good pseudo-arrays. This article will explain in detail what a pseudo-array is and how to convert a pseudo-array into a real array in ES5 and ES6 respectively. What is a pseudo-array? The main characteristic of a pseudo-array: it is an object, and that object has a length property.

 In the JS era a few years ago, there was no concept of modularity. However, as front-end projects become larger and more complex, it is urgent to introduce the concept of modularity. Before ES6, the community developed some modular solutions, such as: CommonJS and AMD and CMD. These are slowly being replaced by import and export after ES6. Export is used to specify the interface that the module opens to the outside world. Regardless of whether you define it or not, the module exported by export is in strict mode and cannot be used in embedded scripts. The import command is used to import functionality provided by other modules.

 JavaScript does not have the concept of classes in languages such as JAVA in the strict sense before ES6. ES6 added class, but in fact this class is just syntactic sugar for constructors and prototypes before ES6. To really understand the most complex parts of JavaScript, you have to start with the initial constructors and prototypes. Prototype is one of the characteristics of JavaScript. Although the object-oriented concepts such as classes and instances are similar to languages such as Java, they are not the same in essence. In JavaScript, each object instantiated by the constructor generally only contains its own properties, but when we call a method or property that is not on the object, the instantiated object will look up its own prototype. . If the prototype has not been found, and the prototype object has its own prototype, it will go back to the top prototype along the prototype chain.

Both async and await are syntaxes provided in es7. Compared with the promise of es6, this method has higher code readability. Literally understand that async means asynchronous, await means waiting, then their role is very obvious: async: declare that a function is asynchronous; await: wait for an asynchronous function to complete execution.

 Generators are a new function control and usage scheme in ES6 that gives you more control over how functions continue, pause, and more. We usually write a lot of functions, and the conditions for these functions to terminate are usually return values or exceptions. Generator functions are also functions, but with a few differences from regular functions. First, generator functions should add the symbol "*" after the function. The generator function can then use the yield keyword to control the execution. Finally, the return value of a generator function is a generator. A generator is actually a special kind of iterator.

 What is an iterator?An iterator is an interface that provides a unified access mechanism for various data structures. Any data structure can complete the traversal operation as long as the iterator interface is deployed.ES6 created a new traversal command for...of loop, which natively has a data structure with the iterator interface (which can be traversed with for...of). Contains Array, Arguments, Set, Map, String, TypedArray, NodeList. Of course, you can also implement this interface manually, which is convenient for practical use.

 This article mainly introduces the usage of ES6 spread operator and rest operator, and analyzes the basic functions, usage and operation precautions of ES6 spread operator and rest operator in combination with examples.

 In ES6, in addition to the new features of let and const, arrow functions are the most frequently used new features. But this feature is not unique to ES6. Arrow functions, as the name suggests, are functions defined using arrows (=>) and belong to a class of anonymous functions. It allows us to write smaller function syntaxes. The code of arrow functions is simpler and more flexible to write.