Why does string to number comparison work in Javascript

Question

I am trying to compare a value coming from a HTML text field with integers. And it works as expected. Condition is -

x >= 1 && x <= 999;

Where x is the value of text field. Condition returns true whenever value is between 1-999 (inclusive), else false. Problem is, that the value coming from the text field is of string type and I'm comparing it with integer types. Is it okay to have this comparison like this or should I use parseInt() to convert x to integer ?

Answer 1

The MDN's docs on Comparision states that the operands are converted to a common type before comparing (with the operator you're using):

The more commonly used abstract comparison (e.g. ==) converts the operands to the same Type before making the comparison. For relational abstract comparisons (e.g., <=), the operands are first converted to primitives, then to the same type, before comparison.

You'd only need to apply parseInt() if you were using a strict comparision, that does not perform the auto casting before comparing.

Answer 2

You should use parseInt if the var is a string. Add = to compare datatype value:

parseInt(x) >== 1 && parseInt(x) <== 999;