JavaScript变量上的点符号

Question

dateNow = new Date()
dateGet = dateNow.getDay()
document.write(dateGet.toDateString())

Why is this document.write(date11.toDateString()) not allowed in JavaScript... date11 is a variable. It gives me an error of "toDateString() is not a function"

Answer 1

Presuming you meant to write dateGet and not date11 in your question:

The problem is that dateGet is not a Date instance-- it is a number that was returned from the getDay() Date method.

 const dateNow = new Date() const dateGet = dateNow.getDay() console.log(dateNow instanceof Date); // true console.log(typeof dateNow.getDay); // function console.log(dateGet instanceof Date); //false console.log(typeof dateGet); // number console.log(typeof dateGet.toDateString); // undefined document.write(dateGet.toDateString()) // 🙁 

Since dateGet is not an instance of Date but is actually a number, it has no such method as .toDateString , so when you attempt to call this non-existent method an error is thrown.

Answer 2

toDateString() is a function for Date objects. dateGet or date11 are actually integers because that's what getDay() returns, so that's by design: toDateString() is not a function of integers . You can either `document.write(dateGet) and that'll return an integer for the day of the week. If you want "monday" or "tuesday", etc. then you'll need to create a small array of days and match to the dateGet.