Code style issues

'var' declared not at the beginning of a function  

.

Chained equality  

.

Chained function call  

.

Constant on left side of comparison  

.

Constant on right side of comparison  

.

Nested function call  

.

Redundant braces around arrow function body  

.

Statement body without braces  

.

Undefined property assignment  

.

Unnecessary parentheses  

.

Unterminated statement  

.