Result of built-in API call should not be ignored when it has no side effect

This rule applies when the result of built-in API call, which has no side effects, is not used.

For example, calling substring API on the string has no side effect on itself. So it is useless if the result is not used.

This is likely to be a programmer's misunderstanding. Therefore, the result should not be ignored or the code should be removed.

This rule also applies to common Lodash APIs without side effects like omit().

	Noncompliant Code Example		Compliant Code Example
1	var s = 'foobar';	1	var s = 'foobar';
2	s.substring(0, 3); // NO_EFFECT_CALL alarm because the return value of 'substring' is not used.	2	var ret = s.substring(0, 3);

Noncompliant Code Example

var s = 'foobar';
s.substring(0, 3); // NO_EFFECT_CALL alarm because the return value of 'substring' is not used.

var s = 'foobar';
var ret = s.substring(0, 3);