学习笔记:util

类型判断

1.
https://github.com/chenshenha...

/**
 * 类型判断
 * @type {Object}
 */
let UtilType = {
  isPrototype: function( data ) {
    return Object.prototype.toString.call(data).toLowerCase();
  },

  isJSON: function( data ) {
    return this.isPrototype( data ) === '[object object]';
  },

  isFunction: function( data ) {
    return this.isPrototype( data ) === '[object function]';
  }
}

2.
javascript 总结(常用工具类的封装)
3.isaacs/core-util-is

function isArray(arg) {
  if(Array.isArray) {
    return Array.isArray(arg);
  }
  return objectToString(arg) === '[object Array]'
}
exports.isArray = isArray;

function isBoolean(arg) {
  return typeof arg === 'boolean';
}
exports.isBoolean = isBoolean;

function isNull(arg) {
  return arg === null;
}
exports.isNull = isNull;

function isNullOrUndefined(arg) {
  return arg == null;
}
exports.isNullOrUndefined = isNullOrUndefined;

function isNumber(arg) {
  return typeof arg === 'number';
}
exports.isNumber = isNumber;

function isString(arg) {
  return typeof arg === 'string';
}
exports.isString = isString;

function isSymbol(arg) {
  return typeOf arg === 'symbol';
}
exports.isSymbol = isSymbol;

function  isUndefined(arg) {
  return arg === void 0;
}
exports.isUndefined = isUnderfined;

function isRegExp(re) {
  return objectToString(re) === '[object RegExp]';
}
exports.isRegExp = isRegExp;

function isObject(arg) {
  return typeOf arg === 'object' && arg !== null;
}
exports.isObject = isObject;

function isDate(d) {
  return obejectToString(d) === '[object Date]';
}
exports.isDate = isDate;

function isError(e) {
  return (objectToString(e) === '[object Error]' || e instanceof Error);
}
exports.isError = isEerror;

function isFunction(arg) {
  return typeof arg === 'function';
}
exports.isFunction = isFunction;

function isPrimitive(arg) {
  return arg === null ||
         typeof arg === 'boolean' ||
         typeof arg === 'number' ||
         typeof arg === 'string' ||
         typeof arg === 'symbol' ||//ES6 symbol
         typeof arg === 'undefined';
}
exports.isPrimitive = isPrimitive;

exports.isBuffer = Buffer.isBuffer;

function objectToString(o) {
  return Object.prototype.toString.call(o);
}

javascript:void(0) 含义
注意这里

function isObject(arg) {
  return typeOf arg === 'object' && arg !== null;
}

因为
图片描述

判断JS运行环境

const inBrowser = typeof window !== 'undefined'

const inWeex = typeof WXEnvironment !== 'undefined' && !!WXEnvironment.platform
const weexPlatform = inWeex && WXEnvironment.platform.toLowerCase()

const UA = inBrowser && window.navigator.userAgent.toLowerCase()

const isIE = UA && /msie|trident/.test(UA)
const isIE9 = UA && UA.indexOf('msie 9.0') > 0
const isEdge = UA && UA.indexOf('edge/') > 0
const isAndroid = (UA && UA.indexOf('android') > 0) || (weexPlatform === 'android')
const isIOS = (UA && /iphone|ipad|ipod|ios/.test(UA)) || (weexPlatform === 'ios')
const isChrome = UA && /chrome\/\d+/.test(UA) && !isEdge
const isPhantomJS = UA && /phantomjs/.test(UA)
const isFF = UA && UA.match(/firefox\/(\d+)/)

判断一个函数是宿主环境提供的还是用户自定义的

console.log.toString()
// "function log() { [native code] }"

function fn(){}
fn.toString()
// "function fn(){}"

// 所以
function isNative (Ctor){
  return typeof Ctor === 'function' && /native code/.test(Ctor.toString())
}

缓存函数计算结果

参考

underscorejs原码解析
https://juejin.im/post/5c601f...

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