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JavaScript Introducing ES2015 The Cooler Parts of ES2015 Rest Parameters and Spread Operator

Swan The Human
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Swan The Human
Full Stack JavaScript Techdegree Student 19,338 Points
Posted by Swan The Human
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Swan The Human
Full Stack JavaScript Techdegree Student 19,338 Points

Could anyone give me a real world example of the use of rest params? What would this be used for

I understand why you would want to use the spread operator for concatenation of arrays but what would you use the rest param in functions for? I get the usage of it but it makes it more clear and useful with an example of one thing you would use it for. Thanks!

1 Answer

Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

Rest parameters are essentially the opposite of spread syntax. Instead of expanding an array into individual arguments, an unspecified number of individual arguments are folded into an array. Example:

// use REST parameter to output any number of messages
function logger(...msgs) {
  console.info(`Logging ${msgs.length} messages:`)
  for (msg of msgs)
    console.log(msg);
}

logger("message one", "message two");
logger("this", "is", "a", "test");

More details and another good example of usage can be found on the MDN Rest Parameters page.