JavaScript the correct way to determine the undefined type
- 2020-06-22 23:46:13
- OfStack
if (reValue== undefined){
alert("undefined");
}
Found that the judgment can not be made, finally checked the data to use typeof
Methods:
if (typeof(reValue) == "undefined") {
alert("undefined");
}
typeof returns a string with six possibilities: "number", "string", "boolean", "object", "function", "undefined"