How to use boolean operators in js-1024programmer

Operation rules: If the first operator returns true, return the value of the second operator (not a Boolean value); if the first If an operator returns false, the first operator is returned, and the second operator is no longer evaluated (short circuit)

// &#  39; a' converted to boolean is true, so directly return the second operator ''
 & # 39; a & # 39; & & & # 39; & # 39;
 // & # 39; & # 39; converted to boolean is false, so return the first operator directly & # 39; & # 39;
 '' && 'a'

Or operator (||)

Or Operators are also used for the value of multiple expressions

Operation rules: If the Boolean value of the first operator is true, then return the value of the first operator directly; if the first operator If the Boolean value of an operator is false, then return the value of the second operator

// Boolean value of ''  is false, so here returns 'b'
 & # 39; & # 39; || & # 39; b & # 39;
 // The boolean value of 'b' is true, so here returns 'b'
 & # 39; b & # 39; || & # 39; & # 39;

The or operator commonly used to set a default value for a variable

Ternary operator

expression1 ? expression2 : expression3;

If the Boolean value of expression1 is true, return expression2; If the Boolean value of expression1 is false, return expression3.

Recommended tutorial: js introductory tutorial

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