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closure structure
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function outerFunction(){ | |
var someCount = 0; | |
return function innerFunction(){ | |
someCount++; | |
console.log("Called ",someCount," times"); | |
} | |
} | |
var counter = outerFunction(); | |
counter(); // "Called 1 times" | |
counter(); // "Called 2 times" | |
//========================================== example | |
function makeBirdCounter() { | |
var count = 0; | |
return function(){ | |
count += 1; | |
return count + ' birds'; | |
} | |
} | |
var birdCounter = makeBirdCounter(); | |
birdCounter(); // "1 birds" | |
birdCounter(); // "2 birds" | |
//========================================== for loop closure example | |
// 3 buttons: First Second Third | |
//<!DOCTYPE html> | |
//<html> | |
//<head> | |
// <title>Array of Loops</title> | |
//</head> | |
//<body> | |
// <button id="first">First</button> | |
// <button id="second">Second</button> | |
// <button id="third">Third</button> | |
//script type="text/javascript" src="setUpHandlers.js"></script> | |
//</body> | |
//</html> | |
var buttons = document.getElementsByTagName('button'); | |
for(var i = 0; i < buttons.length; i += 1) { | |
var button = buttons[i]; | |
var buttonName = button.innerHTML; | |
button.addEventListener('click', function(){ | |
console.log(buttonName); | |
}); | |
} // this will output Third so won't work -> it needs a closure | |
function createHandler(name) { | |
return function(){ | |
console.log(name); | |
} | |
} | |
for(var i = 0; i < buttons.length; i += 1) { | |
var button = buttons[i]; | |
var buttonName = button.innerHTML; | |
button.addEventListener('click', createHandler(buttonName)); | |
} | |
// or use let instead of var | |
for(var i = 0; i < buttons.length; i += 1) { | |
var button = buttons[i]; | |
let buttonName = button.innerHTML; | |
button.addEventListener('click', function(){ | |
console.log(name); | |
}); | |
} | |
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