例子：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Document</title> </head> <body> <script type="text/javascript"> var arr1 = [1, 2, 3, 4, 5] var arr2 = [1, 2, 4, 5] for (var i = 0; i < arr1.length; i++) { if (arr2.indexOf(arr1[i]) === -1) { alert(arr1[i]) //3 } } </script> </body> </html>