JavaScript Archives – Dotneteer's Blog

Date:October 26, 2016Posted By:Istvan NovakCategory:JavaScriptTag:ES 2015, ES6

ES 2015 — New Block-Level Variable Declarations

In contrast to other curly brace programming languages like C, C++, Java, or C#, JavaScript shows some unusual behavior. Take a look at this code snippet:

// Exercise-01-01.js

function getWiggin(childIndex) {
  if (childIndex === 1) {
    var wiggin = 'Peter';
  }
  else if (childIndex === 2) {
    var wiggin = 'Valentine';
  }
  else if (childIndex === 3) {
    wiggin = 'Ender';
  }
  return wiggin;
}

console.log("The First:", getWiggin(1));
console.log("The Second:", getWiggin(2));
console.log("The Third:", getWiggin(3));
console.log("Unknown:", getWiggin(4));

// Exercise-01-01.js

function getWiggin(childIndex) {

if (childIndex === 1) {

var wiggin = 'Peter';

}

else if (childIndex === 2) {

var wiggin = 'Valentine';

}

else if (childIndex === 3) {

wiggin = 'Ender';

}

return wiggin;

}

console.log("The First:", getWiggin(1));

console.log("The Second:", getWiggin(2));

console.log("The Third:", getWiggin(3));

console.log("Unknown:", getWiggin(4));

The multiple declarations of the wiggin variable in getWiggin suggests that the instance within the childIndex === 1 branch is different from the other created in the childIndex === 2 section….

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ES 2015 — New Block-Level Variable Declarations

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