JS开发常用工具函数(小结)(5)

Array.prototype.find = Array.prototype.find || function find(fn, ctx){ fn = fn.bind(ctx) let result; this.some((value, index, arr), thisValue) => { return fn(value, index, arr) ? (result = value, true) : false }) return result }

45、arr.findIndex ：返回数组中通过测试（函数fn内判断）的第一个元素的下标

Array.prototype.findIndex = Array.prototype.findIndex || function findIndex(fn, ctx){ fn = fn.bind(ctx) let result; this.some((value, index, arr), thisValue) => { return fn(value, index, arr) ? (result = index, true) : false }) return result }

46、performance.timing：利用performance.timing进行性能分析

window.onload = function(){ setTimeout(function(){ let t = performance.timing console.log('DNS查询耗时 ：' + (t.domainLookupEnd - t.domainLookupStart).toFixed(0)) console.log('TCP链接耗时 ：' + (t.connectEnd - t.connectStart).toFixed(0)) console.log('request请求耗时 ：' + (t.responseEnd - t.responseStart).toFixed(0)) console.log('解析dom树耗时 ：' + (t.domComplete - t.domInteractive).toFixed(0)) console.log('白屏时间 ：' + (t.responseStart - t.navigationStart).toFixed(0)) console.log('domready时间 ：' + (t.domContentLoadedEventEnd - t.navigationStart).toFixed(0)) console.log('onload时间 ：' + (t.loadEventEnd - t.navigationStart).toFixed(0)) if(t = performance.memory){ console.log('js内存使用占比 ：' + (t.usedJSHeapSize / t.totalJSHeapSize * 100).toFixed(2) + '%') } }) }

47、禁止某些键盘事件

document.addEventListener('keydown', function(event){ return !( 112 == event.keyCode || //F1 123 == event.keyCode || //F12 event.ctrlKey && 82 == event.keyCode || //ctrl + R event.ctrlKey && 78 == event.keyCode || //ctrl + N event.shiftKey && 121 == event.keyCode || //shift + F10 event.altKey && 115 == event.keyCode || //alt + F4 "A" == event.srcElement.tagName && event.shiftKey //shift + 点击a标签 ) || (event.returnValue = false) });

48、禁止右键、选择、复制

['contextmenu', 'selectstart', 'copy'].forEach(function(ev){ document.addEventListener(ev, function(event){ return event.returnValue = false }) });

github地址：https://github.com/hfhan/tools