使用javascript限定符const时，Safari和Chrome的行为不同
[英]Different behavior between safari and chrome when using javascript qualifier `const`
问题描述
i'm very new to javascript. 
我对javascript很陌生。 i'm wondering why the code blow will give two different results between safari and chrome. 我想知道为什么代码打击会在safari和chrome之间给出两个不同的结果。
<!DOCTYPE html>
<html>
<head>
<h1> test </h1>
</head>
<body>
<div id='test'> </div>
<div id='num0' style='display:none'> number one</div>
<div id='num1' style='display:none'> number two</div>
<script type="text/javascript">
for (var i = 0; i <2; i++){
const data = document.getElementById("num"+i).innerHTML;
var newDiv = document.createElement("div");
newDiv.id = i;
newDiv.innerHTML = data;
document.getElementById('test').appendChild(newDiv);
}
</script>
</body>
</html>
safari: 苹果浏览器：
test
number one
number two
chrome: 铬：
test
number one
number one
it seems safari ignored the const qualifier. Safari似乎忽略了const限定词。 is this a undefined behavior? 这是未定义的行为吗？ what happened under the hood? 引擎盖下发生了什么？
1 个解决方案
解决方案1
2 已采纳 2015-09-19 11:06:22
Safari's behavior is right. Safari的行为是正确的。 const is block-scoped, so whenever the loop is repeated, the const -qualified variable of the previous iteration is no longer available, so the new const data declaration can succeed - just like let . const是块作用域的，因此每当重复循环时，先前迭代的const限定变量就不再可用，因此新的const data声明可以成功-就像let一样。 In strict mode, Chrome also behaves like Safari. 在严格模式下，Chrome的行为也类似于Safari。
In non-strict mode, Chrome uses a legacy form of const , where the (const) variable declaration is hoisted and attempts to update the variable are silently ignored. 在非严格模式下，Chrome使用传统形式的const ，其中会提升（const）变量声明，而对变量的更新尝试将被忽略。
Example: 例：
function log(msg) { document.body.appendChild(document.createElement('div')).textContent = msg; } (function() { // Chrome 45 (BAD) : 0 0 0 log('No strict mode'); for (var i = 0; i < 2; ++i) { const data = i; log(data); } try { log(data); // Should fail } catch (e) { log(e); } })(); (function() { // Chrome 45 (GOOD): 0 1 ReferenceError: data is not defined 'use strict'; log('In strict mode'); for (var i = 0; i < 2; ++i) { const data = i; log(data); } try { log(data); // Should fail } catch (e) { log(e); } })();
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