9 powerful mainstream writing methods in JS (various Hack writing methods)-JS Tutorial-php.cn

9 powerful mainstream writing methods in JS (various Hack writing methods)

Guanhui

Release： 2020-05-15 09:28:34

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1. Global replacement

We know that the string function replace () only replaces the first occurrence Condition.

You can replace all occurrences by adding /g at the end of the regular expression.

var example = "potato potato";
console.log(example.replace(/pot/, "tom")); 
// "tomato potato"
console.log(example.replace(/pot/g, "tom")); 
// "tomato tomato"

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2. Extract unique values

By using the Set object and the spread operator, we can create a new array with only unique values.

var entries = [1, 2, 2, 3, 4, 5, 6, 6, 7, 7, 8, 4, 2, 1]
var unique_entries = [...new Set(entries)];
console.log(unique_entries);
// [1, 2, 3, 4, 5, 6, 7, 8]

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3. Convert number to string

We just need to connect a set of empty quotes.

var converted_number = 5 + "";
console.log(converted_number);
// 5
console.log(typeof converted_number); 
// string

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4. Convert string to number

All we need is operator.

One thing to note is that it only applies to "string numbers".

the_string = "123";
console.log(+the_string);
// 123
the_string = "hello";
console.log(+the_string);
// NaN

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5. Randomly arrange the elements in the array

I shuffle the cards every day

var my_list = [1, 2, 3, 4, 5, 6, 7, 8, 9];
console.log(my_list.sort(function() {
    return Math.random() - 0.5
})); 
// [4, 8, 2, 9, 1, 3, 6, 5, 7]

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6. Multidimensional array flattening

Just use the spread operator.

var entries = [1, [2, 5], [6, 7], 9];
var flat_entries = [].concat(...entries); 
// [1, 2, 5, 6, 7, 9]

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7. Short Circuit Condition

Let’s look at this example:

if (available) {
    addToCart();
}

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Just use a variable with a function to shorten it ：

available && addToCart()

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8. Dynamic property names

I always thought that I must first declare an object before assigning dynamic properties.

const dynamic = &#39;flavour&#39;;
var item = {
    name: &#39;Coke&#39;,
    [dynamic]: &#39;Cherry&#39;
}
console.log(item); 
// { name: "Coke", flavour: "Cherry" }

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9. Use length to adjust or clear an array

We mainly rewrite the length of the array.

If we want to adjust the size of the array:

var entries = [1, 2, 3, 4, 5, 6, 7];  
console.log(entries.length); 
// 7  
entries.length = 4;  
console.log(entries.length); 
// 4  
console.log(entries); 
// [1, 2, 3, 4]

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If we want an empty array:

var entries = [1, 2, 3, 4, 5, 6, 7]; 
console.log(entries.length); 
// 7  
entries.length = 0;   
console.log(entries.length); 
// 0 
console.log(entries); 
// []

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