潜在的null / undefined变量的访问属性-javascript

Question

i'm analyzing my code using sonarqube and am running into an issue with the following code:

var backtoyear = $('#backtoyear').val();

if (backtoyear != undefined || backtoyear.length > 0) {
   var currentyear = (new Date()).getFullYear();
   var numberofyears = currentyear - backtoyear;
}

the backtoyear.length variable is causing an "TypeError can be thrown as "backtoyear" might be null or undefined here." because it could potential be null/undefined and therefore won't have any properties.

should i just remove the second have of the OR from the if condition?

Answer 1

You can simplify your following statement,

if (backtoyear != undefined || backtoyear.length > 0) {

to

if (backtoyear) {

This is more readable, efficient and understandable.

Refer to this specification ToBoolean