算法
数组去重
function uniq(arr) {
return [...new Set(arr)]
}
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取交集
let a = new Set([1, 2, 3]);
let b = new Set([4, 3, 2]);
let intersect = new Set([...a].filter(x => b.has(x)));
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取多个数组的交集
var intersection = function(...args) {
if (args.length === 0) {
return []
}
if (args.length === 1) {
return args[0]
}
return [...new Set(args.reduce((result, arg) => {
return result.filter(item => arg.includes(item))
}))]
};
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取差集
let a = new Set([1, 2, 3]);
let b = new Set([4, 3, 2]);
let difference = new Set([...a].filter(x => !b.has(x)));
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最快捷的数组求最大值 ?
var arr = [ 1,5,1,7,5,9];
Math.max(...arr); // 9
//or
Math.max.apply(Math, arr);
//or
Math.max.call(Math, ...arr);
//or
Math.max.bind(Math, ...arr)();
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数组扁平化
reduce递归：
function flattenDeep (arr) {
return arr.reduce((acc, val) =>
Array.isArray(val)
? acc.concat(flattenDeep(val))
: acc.concat(val),
[]);
}
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迭代：
const flatten = function (arr) {
while (arr.some(item => Array.isArray(item))) {
arr = [].concat(...arr)
}
return arr
}
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toString: 只适用于简单数组
function flatten (arr){
return arr.toString().split(',');
//return arr.join(',').split(',').map(item => Number(item))
}
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ES10:
arr.flat(Infinity);
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数字转中文
function money2Chinese(num) {
if(typeof num !== 'number') {
throw new Error('参数为数字')
};
let strOutput = "";
let strUnit = '仟佰拾亿仟佰拾万仟佰拾元角分';
num += "00";
const intPos = num.indexOf('.');
if (intPos >= 0) {
num = num.substring(0, intPos) + num.substr(intPos + 1, 2);
}
strUnit = strUnit.substr(strUnit.length - num.length);
for (let i = 0; i < num.length; i++) {
strOutput += '零壹贰叁肆伍陆柒捌玖'.substr(num.substr(i, 1), 1) + strUnit.substr(i, 1);
}
return strOutput.replace(/零角零分$/, '整').replace(/零[仟佰拾]/g, '零').replace(/零{2,}/g, '零').replace(/零([亿|万])/g, '$1').replace(/零+元/, '元').replace(/亿零{0,3}万/, '亿').replace(/^元/, "零元");
}
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驼峰写法转下划线写法
function camelCaseToUnderline (name) {
if (typeof name !== 'string') {
throw TypeError('传入参数不正确, 要求为字符串类型');
}
return name.replace(/[A-Z]/g, function (val, index) {
let char = val.toLowerCase();
// 首字母为大写时无需加入下划线
return index === 0 ? char : '_' + char;
})
}
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下划线写法转驼峰写法
function underlineToCamelCase (s) {
return s.replace(/-\w/g, function(x) {
return x.slice(1).toUpperCase();
})
}
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