What are the basic data types in es6

async is es7. async and await are new additions to ES7 and are solutions for asynchronous operations; async/await can be said to be syntactic sugar for co modules and generator functions, solving js asynchronous code with clearer semantics. As the name suggests, async means "asynchronous". Async is used to declare that a function is asynchronous; there is a strict rule between async and await. Both cannot be separated from each other, and await can only be written in async functions.

For browser compatibility. As a new specification for JS, ES6 adds a lot of new syntax and API. However, modern browsers do not have high support for the new features of ES6, so ES6 code needs to be converted to ES5 code. In the WeChat web developer tools, babel is used by default to convert the developer's ES6 syntax code into ES5 code that is well supported by all three terminals, helping developers solve development problems caused by different environments; only in the project Just configure and check the "ES6 to ES5" option.

In es5, you can use the for statement and indexOf() function to achieve array deduplication. The syntax "for(i=0;i<array length;i++){a=newArr.indexOf(arr[i]);if(a== -1){...}}". In es6, you can use the spread operator, Array.from() and Set to remove duplication; you need to first convert the array into a Set object to remove duplication, and then use the spread operator or the Array.from() function to convert the Set object back to an array. Just group.

The basic data types of plc include bits, bytes, integers, floating point numbers, strings, Boolean, time, counters, timers, etc. Detailed introduction: 1. Bit: represents a switch state, which can be 0 or 1; 2. Byte: represents 8-bit data, which can store integer values ​​(0-255) or characters; 3. Integer (Integer): represents a signed integer value, which can be a positive number, a negative number, or zero; 4. Float (Float): represents a real value with a decimal part, which can be single precision (32 bits) or double precision (64 bits) )wait

In es6, the temporary dead zone is a syntax error, which refers to the let and const commands that make the block form a closed scope. Within a code block, before a variable is declared using the let/const command, the variable is unavailable and belongs to the variable's "dead zone" before the variable is declared; this is syntactically called a "temporary dead zone". ES6 stipulates that variable promotion does not occur in temporary dead zones and let and const statements, mainly to reduce runtime errors and prevent the variable from being used before it is declared, resulting in unexpected behavior.

Basic data types have the characteristics of fixed size, fixed value range, immutability, direct access to memory, default value, operation rules, occupied storage space, speed, special functions and conversions. Detailed introduction: 1. Fixed size. Basic data types have a fixed size when declared, which means that the storage space of each basic data type is the same under any circumstances and will not change due to the value of the variable; 2. Fixed value range, each basic data type has a fixed value range; 3. Immutability, basic data types are immutable, etc.

In ES6, you can use the length attribute of the array object to determine how many items there are in the array, that is, to get the number of elements in the array; this attribute can return the number of elements in the array, just use the "array.length" statement. Returns a value representing the number of elements of the array object, that is, the length value.

ES6 import will cause variable promotion. Variable hoisting is the promotion of a variable declaration to the very beginning of its scope. js has to go through the compilation and execution phases. During the compilation phase, all variable declarations will be collected and variables declared in advance, and other statements will not change their order. Therefore, during the compilation phase, the first step is already is executed, and the second part is executed only when the statement is executed in the execution phase.