字符串处理的基础知识.md

字符串转为小写字母str.toLowerCase()转为大写字母str.toUpperCase()

str.toLowerCase()
str.toUpperCase()

补全字符串 str.padEnd() str.padStart()

let str = 'abc'
console.log(str.padEnd(10,'*')); // 'abc*******'
console.log(str.padStart(10,'*')); // '*******abc'

截取字符串 str.substring(from, to)

let str = 'abc111fdnjsnds'
console.log(str.substring(0, 1)); // 'a'
console.log(str.substring(1, 1)); // ''
console.log(str.substring(1, 2)); // 'b'
console.log(str.substring(2, 8)); // 'c111fd'

截取字符串 str.substr(start, length)

let str = 'abc111fdnjsnds'
console.log(str.substr(0, 1)); // 'a'
console.log(str.substr(1, 1)); // 'b'
console.log(str.substr(1, 2)); // 'bc'
console.log(str.substr(2, 8)); // 'c111fdnj'

ASCII码转换 charCodeAt fromCharCode

let a = '0',
b='9',
c='A',
d='Z',
e='a',
f='z';
console.log(a.charCodeAt(0)); // 48
console.log(b.charCodeAt(0)); // 57
console.log(c.charCodeAt(0)); // 65
console.log(d.charCodeAt(0)); // 90
console.log(e.charCodeAt(0)); // 97
console.log(f.charCodeAt(0)); // 122

console.log(String.fromCharCode(48, 57, 65, 90, 97, 122)); // '09AZaz'

二维数组

let a = new Array(m).fill(0).map(x => x = new Array(n).fill(0))