i：表示匹配时不区分大小写

Str = "JavaScript is different from java";

reg = /java\w*/i;

arr_m = str.match(reg);//arr_m = ["JavaScript"]

g：表示执行全局匹配

Str = "JavaScript is different from java";

reg = /java\w*/ig;

arr_m = str.match(reg);//arr_m = ["JavaScript"]

m：表示采用多行模式执行匹配

在多行模式时，^表示一行的开头或者字符串的开头，$表示一行的结尾（换行）或者字符串的结尾

str = "JavaScript is different from java They are different";

reg = /\w+$/;

arr_m = str.match(reg);//arr_m = ["different"]

str = "JavaScript is different from java\nThey are different";

reg = /\w+$/;

arr_m = str.match(reg);//arr_m = ["different"]

str = "JavaScript is different from java\nThey are different";

reg = /\w+$/mg;

arr_m = str.match(reg);//arr_m = ["java","different"]

str = "JavaScript is different from java\njavascript and java are different.";

reg1 = /(^java\w*)|(java)/ig;

reg2 = /(^java\w*)|(java)/img;

arr_m1 = str.match(reg);//arr_m1 = ["JavaScript"]

arr_m2 = str.match(reg);//arr_m2 = ["JavaScript","java","javascript "]

JavaScript正则表达式-后缀选项（标记）