JavaScript In Practice: ES6 And Beyond/

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The ES6 way

The ES6 way

default values and using a variable number of arguments in functions

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ES6 supports default values. Whenever an argument is not given, the default value is substituted. The syntax is quite compact:

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function addCalendarEntry( 
    event, 
    date = new Date().getTime(), 
    len = 60, 
    timeout = 1000 ) {
    return len;
}
var add=addCalendarEntry( 'meeting' );
console.log(add); //outputs the default value set earlier

Suppose function f is given with two arguments, a and b. ...