摘要：
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>Title</title> <script> var num1 ="3.14" var ret1 = parseFloat(num1) // #将字符串转换为数字 阅读全文
摘要：
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>Title</title> <script> // undefined场景1 var a; console.log(a,typeof a) // undefined 阅读全文
摘要：
知识点1：除数字0和字符串为空外全是true<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>Title</title> <script> var ret = 2 > 1 console.log(ret,typeo 阅读全文