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henser
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With ES6 now widely supported, the best answer to this question has changed. ES6 provides the let and const keywords for this exact circumstance. Instead of messing around with closures, we can just use let to set a loop scope variable like this:

var funcs = [];
for (let i = 0; i < 3; i++) { 
 funcs[i] = function() { 
 console.log("My value: " + i); 
 };
}

val will then point to an object that is specific to that particular turn of the loop, and will return the correct value without the additional closure notation. This obviously significantly simplifies this problem.

const is similar to let with the additional restriction that the variable name can't be rebound to a new reference after initial assignment.

Browser support is now here for those targeting the latest versions of browsers. const/let are currently supported in the latest Firefox, Safari, Edge and Chrome. It also is supported in Node, and you can use it anywhere by taking advantage of build tools like Babel. You can see a working example here: http://jsfiddle.net/ben336/rbU4t/2/

Docs here:

Beware, though, that IE9-IE11 and Edge prior to Edge 14 support let but get the above wrong (they don't create a new i each time, so all the functions above would log 3 like they would if we used var). Edge 14 finally gets it right.

With ES6 now widely supported, the best answer to this question has changed. ES6 provides the let and const keywords for this exact circumstance. Instead of messing around with closures, we can just use let to set a loop scope variable like this:

var funcs = [];
for (let i = 0; i < 3; i++) { 
 funcs[i] = function() { 
 console.log("My value: " + i); 
 };
}

val will then point to an object that is specific to that particular turn of the loop, and will return the correct value without the additional closure notation. This obviously significantly simplifies this problem.

const is similar to let with the additional restriction that the variable name can't be rebound to a new reference after initial assignment.

Browser support is now here for those targeting the latest versions of browsers. const/let are currently supported in the latest Firefox, Safari, Edge and Chrome. It also is supported in Node, and you can use it anywhere by taking advantage of build tools like Babel. You can see a working example here: http://jsfiddle.net/ben336/rbU4t/2/

Docs here:

Beware, though, that IE9-IE11 and Edge prior to Edge 14 support let but get the above wrong (they don't create a new i each time, so all the functions above would log 3 like they would if we used var). Edge 14 finally gets it right.

With ES6 now widely supported, the best answer to this question has changed. ES6 provides the let and const keywords for this exact circumstance. Instead of messing around with closures, we can just use let to set a loop scope variable like this:

var funcs = [];
for (let i = 0; i < 3; i++) { 
 funcs[i] = function() { 
 console.log("My value: " + i); 
 };
}

val will then point to an object that is specific to that particular turn of the loop, and will return the correct value without the additional closure notation. This obviously significantly simplifies this problem.

const is similar to let with the additional restriction that the variable name can't be rebound to a new reference after initial assignment.

Browser support is now here for those targeting the latest versions of browsers. const/let are currently supported in the latest Firefox, Safari, Edge and Chrome. It also is supported in Node, and you can use it anywhere by taking advantage of build tools like Babel. You can see a working example here: http://jsfiddle.net/ben336/rbU4t/2/

Docs here:

Beware, though, that IE9-IE11 and Edge prior to Edge 14 support let but get the above wrong (they don't create a new i each time, so all the functions above would log 3 like they would if we used var). Edge 14 finally gets it right.

With ES6 now widely supported, the best answer to this question has changed. ES6 provides the let and const keywords for this exact circumstance. Instead of messing around with closures, we can just use let to set a loop scope variable like this:

var funcs = [];
for (let i = 0; i < 3; i++) { 
 funcs[i] = function() { 
 console.log("My value: " + i); 
 };
}

var funcs = [];
 for (let i = 0; i < 3; i++) { 
 funcs[i] = function() { 
 console.log("My value: " + i); 
 };
 }

val will then point to an object that is specific to that particular turn of the loop, and will return the correct value without the additional closure notation. This obviously significantly simplifies this problem.

const is similar to let with the additional restriction that the variable name can't be rebound to a new reference after initial assignment.

Browser support is now here for those targeting the latest versions of browsers. const/let are currently supported in the latest Firefox, Safari, Edge and Chrome. It also is supported in Node, and you can use it anywhere by taking advantage of build tools like Babel. You can see a working example here: http://jsfiddle.net/ben336/rbU4t/2/

Docs here:

Beware, though, that IE9-IE11 and Edge prior to Edge 14 support let but get the above wrong (they don't create a new i each time, so all the functions above would log 3 like they would if we used var). Edge 14 finally gets it right.

With ES6 now widely supported, the best answer to this question has changed. ES6 provides the let and const keywords for this exact circumstance. Instead of messing around with closures, we can just use let to set a loop scope variable like this:

var funcs = [];
for (let i = 0; i < 3; i++) { 
 funcs[i] = function() { 
 console.log("My value: " + i); 
 };
}

val will then point to an object that is specific to that particular turn of the loop, and will return the correct value without the additional closure notation. This obviously significantly simplifies this problem.

const is similar to let with the additional restriction that the variable name can't be rebound to a new reference after initial assignment.

Browser support is now here for those targeting the latest versions of browsers. const/let are currently supported in the latest Firefox, Safari, Edge and Chrome. It also is supported in Node, and you can use it anywhere by taking advantage of build tools like Babel. You can see a working example here: http://jsfiddle.net/ben336/rbU4t/2/

Docs here:

Beware, though, that IE9-IE11 and Edge prior to Edge 14 support let but get the above wrong (they don't create a new i each time, so all the functions above would log 3 like they would if we used var). Edge 14 finally gets it right.

With ES6 now widely supported, the best answer to this question has changed. ES6 provides the let and const keywords for this exact circumstance. Instead of messing around with closures, we can just use let to set a loop scope variable like this:

var funcs = [];
 for (let i = 0; i < 3; i++) { 
 funcs[i] = function() { 
 console.log("My value: " + i); 
 };
 }

val will then point to an object that is specific to that particular turn of the loop, and will return the correct value without the additional closure notation. This obviously significantly simplifies this problem.

const is similar to let with the additional restriction that the variable name can't be rebound to a new reference after initial assignment.

Browser support is now here for those targeting the latest versions of browsers. const/let are currently supported in the latest Firefox, Safari, Edge and Chrome. It also is supported in Node, and you can use it anywhere by taking advantage of build tools like Babel. You can see a working example here: http://jsfiddle.net/ben336/rbU4t/2/

Docs here:

Beware, though, that IE9-IE11 and Edge prior to Edge 14 support let but get the above wrong (they don't create a new i each time, so all the functions above would log 3 like they would if we used var). Edge 14 finally gets it right.

Rollback to Revision 6 - Edit approval overridden by post owner or moderator
Source Link
Ben McCormick
  • 25.8k
  • 12
  • 56
  • 71

With ES6 now widely supported, the best answer to this question has changed. ES6 provides the let and const keywords for this exact circumstance. Instead of messing around with closures, we can just use let to set a loop scope variable like this:

var funcs = [];
for (let i = 0; i < 3; i++) { 
 funcs[i] = function() { 
 console.log("My value: " + i); 
 };
}

val will then point to an object that is specific to that particular turn of the loop, and will return the correct value without the additional closure notation. This obviously significantly simplifies this problem.

const is similar to let with the additional restriction that the variable name can't be rebound to a new reference after initial assignment.

Browser support is nowherenow here for those targeting the latest versions of browsers. const/let are currently supported in the latest Firefox, Safari, Edge, and Chrome. It also is supported in Node, and you can use it anywhere by taking advantage of build tools like Babel. You can see a working example here: http://jsfiddle.net/ben336/rbU4t/2/

Docs here:

Beware, though, that IE9-IE11 and Edge prior to Edge 14 support let but get the above wrong (they don't create a new i each time, so all the functions above would log 3 like they would if we used var). Edge 14 finally gets it right.

With ES6 now widely supported, the best answer to this question has changed. ES6 provides the let and const keywords for this exact circumstance. Instead of messing around with closures, we can just use let to set a loop scope variable like this:

var funcs = [];
for (let i = 0; i < 3; i++) { 
 funcs[i] = function() { 
 console.log("My value: " + i); 
 };
}

val will then point to an object that is specific to that particular turn of the loop and will return the correct value without the additional closure notation. This obviously significantly simplifies this problem.

const is similar to let with the additional restriction that the variable name can't be rebound to a new reference after initial assignment.

Browser support is nowhere for those targeting the latest versions of browsers. const/let are currently supported in the latest Firefox, Safari, Edge, and Chrome. It also is supported in Node, and you can use it anywhere by taking advantage of build tools like Babel. You can see a working example here: http://jsfiddle.net/ben336/rbU4t/2/

Docs here:

Beware, though, that IE9-IE11 and Edge prior to Edge 14 support let but get the above wrong (they don't create a new i each time, so all the functions above would log 3 like they would if we used var). Edge 14 finally gets it right.

With ES6 now widely supported, the best answer to this question has changed. ES6 provides the let and const keywords for this exact circumstance. Instead of messing around with closures, we can just use let to set a loop scope variable like this:

var funcs = [];
for (let i = 0; i < 3; i++) { 
 funcs[i] = function() { 
 console.log("My value: " + i); 
 };
}

val will then point to an object that is specific to that particular turn of the loop, and will return the correct value without the additional closure notation. This obviously significantly simplifies this problem.

const is similar to let with the additional restriction that the variable name can't be rebound to a new reference after initial assignment.

Browser support is now here for those targeting the latest versions of browsers. const/let are currently supported in the latest Firefox, Safari, Edge and Chrome. It also is supported in Node, and you can use it anywhere by taking advantage of build tools like Babel. You can see a working example here: http://jsfiddle.net/ben336/rbU4t/2/

Docs here:

Beware, though, that IE9-IE11 and Edge prior to Edge 14 support let but get the above wrong (they don't create a new i each time, so all the functions above would log 3 like they would if we used var). Edge 14 finally gets it right.

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Update to reflect much wider ES6 support these days
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Ben McCormick
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warning about IE9-IE11 and Edge < 14
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T.J. Crowder
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added a reference to const
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Ben McCormick
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deleted 10 characters in body
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Ben McCormick
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deleted 24 characters in body
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nickf
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Ben McCormick
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AltStyle によって変換されたページ (->オリジナル) /