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Javascript boolean operators

The and-operator (&&) and the or-operator (||) employ short-circuiting to prevent unnecessary work if the outcome of the operation does not change with the extra work.

In x && y, y will not be evaluated if x evaluates to false, because the whole expression is guaranteed to be false.

In x || y, y will not be evaluated if x evaluated to true, because the whole expression is guaranteed to be true.


function T() { // True
 return true;
function F() { // False
 return false;


T() && F();



Example 2

F() && T();



Example 3

T() || F();



Example 4

F() || T();




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