<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟教程(runoob.com)</title> </head> <body> <p> typeof 操作符返回变量、对象、函数、表达式的类型。</p> <p id="demo"></p> <script> document.getElementById("demo").innerHTML = typeof "john" + "<br>" + typeof 3.14 + "<br>" + typeof NaN + "<br>" + typeof false + "<br>" + typeof [1,2,3,4] + "<br>" + typeof {name:'john', age:34} + "<br>" + typeof new Date() + "<br>" + typeof function () {} + "<br>" + typeof myCar + "<br>" + typeof null; </script> </body> </html>
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟教程(runoob.com)</title> </head> <body> <p> constructor 属性返回变量或对象的构造函数。</p> <p id="demo"></p> <script> document.getElementById("demo").innerHTML = "john".constructor + "<br>" + (3.14).constructor + "<br>" + false.constructor + "<br>" + [1,2,3,4].constructor + "<br>" + {name:'john', age:34}.constructor + "<br>" + new Date().constructor + "<br>" + function () {}.constructor; </script> </body> </html>
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟教程(runoob.com)</title> </head> <body> <p>判断是否为数组。</p> <p id="demo"></p> <script> var fruits = ["Banana", "Orange", "Apple", "Mango"]; document.getElementById("demo").innerHTML = isArray(fruits); function isArray(myArray) { return myArray.constructor.toString().indexOf("Array") > -1; } </script> </body> </html>
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟教程(runoob.com)</title> </head> <body> <p>判断是否为日期。</p> <p id="demo"></p> <script> var myDate = new Date(); document.getElementById("demo").innerHTML = isDate(myDate); function isDate(myDate) { return myDate.constructor.toString().indexOf("Date") > -1; } </script> </body> </html>
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟教程(runoob.com)</title> </head> <body> <p> String() 方法可以将数字转换为字符串。</p> <p id="demo"></p> <script> var x = 123; document.getElementById("demo").innerHTML = String(x) + "<br>" + String(123) + "<br>" + String(100 + 23); </script> </body> </html>
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟教程(runoob.com)</title> </head> <body> <p>toString() 方法将数字转换为字符串。</p> <p id="demo"></p> <script> var x = 123; document.getElementById("demo").innerHTML = x.toString() + "<br>" + (123).toString() + "<br>" + (100 + 23).toString(); </script> </body> </html>
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟教程(runoob.com)</title> </head> <body> <p> typeof 操作符返回变量或表达式的类型。</p> <button onclick="myFunction()">点我</button> <p id="demo"></p> <script> function myFunction() { var y = "5"; var x = + y; document.getElementById("demo").innerHTML = typeof y + "<br>" + typeof x; } </script> </body> </html>
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>菜鸟教程(runoob.com)</title> </head> <body> <p> typeof 操作符返回变量或表达式的类型。</p> <button onclick="myFunction()">点我</button> <p id="demo"></p> <script> function myFunction() { var y = "John"; var x = + y; document.getElementById("demo").innerHTML = typeof x + "<br>" + x; } </script> </body> </html>
