preface

Manipulation of strings or arrays is often involved in project development. This article summarizes the commonly used JS methods in the project, which can be quickly referred to when it is convenient to meet again.

Array common methods

1. indexOf

The indexOf() method returns the first index in the array where a given element can be found, or -1 if none exists.

const beasts = ["ant"."bison"."camel"."duck"."bison"];
console.log(beasts.indexOf("bison"));  / / 1
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You can specify the starting position: arr.indexof (searchElement[, fromIndex])

console.log(beasts.indexOf("bison".2));  / / 4
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2. filter

The filter() method creates a new array containing all the elements of the test implemented through the provided function. The popular way of thinking about it is to find the matching elements and then filter them out and discard them.

const beasts = ["ant"."bison"."camel"."duck"."bison"];
const beasts_filter = beasts.filter((item) = > item.indexOf("bison"));
console.log(beasts_filter);  // ["ant","camel","duck"]
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3. slice

Gets the range element of the specified index array

const url_array = ["http://www"."baidu"."com"]
const url_array_slice = url_array.slice(1.2);
console.log(url_array_slice);  // ["baidu"]
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4. join

The join() method joins all the elements of an array into a string and returns the string.

const url_array = ["http://www"."baidu"."com"];
const url = url_array.join(".");
console.log(url);  // "http://www.baidu.com"
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String common methods

1. split

Splits a string into an array of strings

const url = "http://www.baidu.com";
const url_array = url.split(".");
console.log(url_array);  // ["http://www","baidu","com"]
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2. substr

String interception

const res = "helloworld";
const res_sub = res.substr(5.9);
console.log(res_sub);  // "world"
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3. parseInt

String to number parseInt(“10”)

Reference documentation

  • MDN Web Docs

tool

Online debugging JS tool: CodePen