What does ? : mean in Javascript? [duplicate]

This question already has answers here: 开发者_开发百科 Question mark and colon in JavaScript (8 answers) Closed 7 years ago.

What does this line of code do?

len = ( s.length>t.length ) ? s.length : t.length

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?: is the ternary operator. It returns a value based on a condition.

x = (condition)?(if-true):(if-false)

So if condition is true, x is the value in the if-true section, and if it's false, then x is the value in if-false.

If is equivalent to what Corv1nus said earlier.

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It's the equivalent of len = Math.max( s.length, t.length ); using the ternary conditional operator.

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It sets the variable len to the length of string s, or the length of string t, depending on which is longer.

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If s.length is greater than t.length set len = s.length else set len = t.length

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That is using the conditional operator, which is also known as a ternary because it takes three operands.

See https://developer.mozilla.org/en/JavaScript/Reference/Operators/Special_Operators/Conditional_Operator for more info.

You can find this construct with the same syntax in PHP, C, C++ and other languages, too.

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it is the equivalent of:

var len=0;
if(s.length>t.length)
  len= s.length;
else
  len=t.length;

So it's just a short way do doing if else.

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len will be assigned the length of either s or t depending on which one has a greater length

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It is doing this:

if (s.length > t.length) {
    len = s.length;
} else {
    len = t.length;
}

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If the length of s is greather than the length of t, make "len" the length of s. If the length of s is less than or equal to the length of t, make "len" the length of t.