语法:
基本类型:字符串(String)、数字(Number)、布尔(Boolean)、对空(Null)、未定义(Undefined)、Symbol。
引用数据类型:对象(Object)、数组(Array)、函数(Function)。
<!DOCTYPE html> <!--基本数据类型--> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script> var num = 10; var str = "hello world"; var boole = true; var array = [10,20,"三十"]; <!--数组通过索引取值--> for (var i=0;i<=array.length;i++){ var result = array[i]; alert(result); } <!--json通过键取值--> var json = {"name":"张三", "age":23} alert(json.name) </script> </body> </html>
函数:
<!DOCTYPE html> <!--函数学习--> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script> function add(a,b) { return a+b; } var result = add(3,6); alert(result); </script> </body> </html>
常见错误:引用错误,变量is not defined
for循环:
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script> for (var i = 1;i<=3;i++){ alert(i); } </script> </body> </html>
常见错误:语法错误,syntaxError
条件语句:if,else if ,else:
<!DOCTYPE html> <!--条件语句--> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> </head> <body> <script> function grade(scrce) { if (scrce>=80){ alert("优秀"); } else if (scrce<80 && scrce>=60){ alert("良好"); } else { alert("不及格") } } grade(80); </script> </body> </html>
js打印九九乘法表:
<script> for (var i = 1;i<=9;i++){ for (var j = 1;j<=i;j++){ document.write(i + "*" + j + "=" + j * i," "); } document.write("<br>"); } </script>
效果如图: