Special case where the variable value is 0 when judging variables in JavaScript

Sometimes we will directly determine the value of the variable in JS, here are a few things:

 var  a = 0;  var  b = 1;  var  c = ' 

In the above case we c,d have no value, so the result is null, but the value of a is 0, the result is also null, here is a special case, 0 in JavaScript judgment is false, so here the result is null, Therefore, we should consider this situation when we make the variable judgment, lest the value of the variable is 0 o'clock, the code in the previous project is judged here, resulting in a variable of 0 being assigned to NULL, the result of this parameter is not passed in, resulting in a program error.

Special case where the variable value is 0 when judging variables in JavaScript