Difference between “!= true” and “== false”?

问题

Are there any technical/logical differences between the comparison "!= true" and "== false" in programming languages, and if there are, which comparison should be chosen on what occasion?

回答1:

Logically there can be differences depending on the type of value that you are comparing and language you are using. For example:

x == false implies x != true, but x != true does not always imply x == false because x can also be some nonsense value.

1 + 1 = 3 is both == false and != true.

7 > cat is neither == false and != true since it is nonsense.

x = null is != true but is not == false.

回答2:

Use accordingly what your code block is expecting.

e.g.

• if your code block is expecting true then use if( true == fun() ) { // your code }.
• if your code block is expecting any value except false then use if( false != fun() ) { // your code }.

来源：https://stackoverflow.com/questions/41682691/difference-between-true-and-false