Tips on using ES6/JavaScript (detailed tutorial)
This article mainly explains to you the skills of using ES6/JavaScript. Friends in need can refer to it.
There are some methods and techniques when writing JavaScript code. Although sometimes all roads lead to Rome, there may always be the shortest path to take. This article will share with you some tips that everyone knows but don’t use very often
Some tips
1.new Set()
To deduplicate arrays, I feel in the 'subconscious' mind that we should loop and compare to deduplicate. In fact, ES6 provides a new data structure Set, which can be used to easily deduplicate arrays, such as:
let arr = [1,1, 2, 2, 3, 3]; let set = new Set(arr); // let newArr = Array.from(set); // Array.from方法可以将 Set 结构转为数组。 console.log(newArr); // [1, 2, 3]
2.Object.assign()
is also an extension method of objects provided in ES6, which can be used to merge and copy objects, like Object merging was also very cumbersome before, but now it is very easy, for example:
let obj1 = {a: 1};
let obj2 = {b: 2};
let obj3 = Object.assign({}, obj1, obj2);
console.log(obj3); // {a: 1, b: 2}3.map()
map method is used for traversal Arrays, with return values, can operate on each item of the array and generate a new array. Sometimes they can replace for and forEach loops to simplify the code, such as:
let arr3 = [1, 2, 3, 4, 5]; let newArr3 = arr3.map((e, i) => e * 10); // 给数组每一项乘以10 console.log(newArr3); // [10, 20, 30, 40, 50]
4 .filter()
The filter method is also used to traverse the array. As the name suggests, it filters the array, triggers a callback function after each element, and retains or removes the current item through judgment. , and finally returns a new array, such as:
let arr4 = [1, 2, 3, 4, 5]; let newArr4 = arr4.filter((e, i) => e % 2 === 0); // 取模，过滤余数不为0的数 console.log(newArr4); // [2，4]
5.some()
#some method is used to traverse the array, in each A callback function is triggered after the item element. As long as one meets the conditions, it will return true, otherwise it will return false, similar to || comparison, for example:
let arr5 = [{result: true}, {result: false}];
let newArr5 = arr5.some((e, i) => e.result); // 只要一个为true，即为true
console.log(newArr5); // true6.every() //With 5 The opposite
every method is used to traverse the array and trigger a callback function after each element. As long as one does not meet the condition, it returns false, otherwise it returns true, similar to && comparison. For example:
let arr6 = [{result: true}, {result: false}];
let newArr6 = arr6.every((e, i) => e.result); // 只要一个为false，即为false
console.log(newArr6); // false7. Ternary operator
This operator should be familiar to everyone, and it can be simplified if else when written silently. The way of writing, for example:
let e = true,
f = '';
if (e) {
f = 'aaa';
} else {
f = 'bbb';
}
// 等同于
f = e ? 'aaa' : 'bbb';8.~~operator
~ symbol is used in JavaScript to perform bitwise negation. ~~It means inverting twice, and the operation value of bit operation is required to be an integer, and the result is also an integer, so the bit operation will automatically become an integer, and the decimal part can be cleverly removed, similar to parseInt, such as:
let a = 1.23; let b = -1.23; console.log(~~a); // 1 console.log(~~b); // -1
The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.
Related articles:
How to use the Node layer to implement multipart form file upload
How to use React to encapsulate Portal reusable components
How to send requests to the intermediate service layer in node (detailed tutorial)
How to obtain Excel content in Node
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