javascript: define a variable in a function

 

This question already has an answer here:

  • Is there a better way to do optional function parameters in JavaScript? [duplicate] 29 answers

    • Try this 

    var myFunction = function(variable) {
  variable = variable || 0;
  // this variant works for all falsy values "", false, null, undefined...
  // if you need check only undefiend, use this variant 
  // variable = typeof(variable) == 'undefined' ? 0 : variable
};

    Default function parameters will be in ES6; ES5 does not allow it.

    With ECMAScript 6 you can do this.

    Check an example: 

    function multiply(a, b = 1) {
  return a*b;
}

multiply(5); // 5

    But this is still experimental and today is only supported by Mozilla Firefox browser.

    Check this link do see documentantion:

    https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Default_parameters#Browser_compatibility

    链接地址: http://www.djcxy.com/p/17280.html

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