?

8>5?true:false;
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Conditions? Value 1: value 2 means 8 is greater than 5? Greater is true and greater is false, right? If the condition in front of number is true, the first value is executed; if not, the second value is executed.

&&

  1. The result is true only if both conditions are true;
  2. If one of them is false, the result is false;
  3. When the first condition is false, the next condition is not judged
 let a = 1,
     b = 2
 let result = a && b 
 console.log(result) / / 2
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Note: If the result is true, the second true value will be returned; If the result is false, the first false value is returned

||

If either condition is true, the result is true. If both conditions are false, the result is false. When a condition is true, subsequent conditions are not judged

 let a,
     b=2
 let result = a || b 
 console.log(result) / / 2
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Note: when a value is involved in a logic or operation, the result is true, and the first true value is returned; If the result is false, the second false value is returned;

!

When the condition is false, the result is true; And vice versa.

Expression a && expression b:

  • Evaluate the result of expression A (or function),
  • If True, the expression b (or function) is executed and the result of b is returned
  • If False, return the result of a;

Expression a | | b:

  • Evaluate the result of expression A (or function),
  • If Fasle, the expression b (or function) is executed and the result of b is returned;
  • If True, return the result of a;