这是我在使用 const 时得到的错误: <error line="2" column="1" severity="warning" message="'const' is available in ES6 (use esnext option) or Mozilla JS extensions (use moz)." source="jshint.W104" /> 我的代码如下所示: const Suites = { Spade: 1, Heart: 2, Diamond: ...
你应该添加parserOptions到你的.eslintrc.json文件
// Uncaught TypeError: f is not a function 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 上面的代码在 ES6 浏览器中,都会报错。 原来,如果改变了块级作用域内声明的函数的处理规则,显然会对老代码产生很大影响。为了减轻因此产生的不兼容问题,ES6 在附录 B里面规定,浏览器的实现可以不遵守上面的...
it("can shadow outer declaration",function(){ const x= 12;vardoWork =function(){ let x= 10;returnx; };varresult =doWork(); expect(result).toBe(10);//trueexpect(x).toBe(12);//true}); it("const also has block scope",function(){if(true){ const x= 12;//SyntaxError, x is no...
They're especially awkward in a language where everything is an expression. Bikeshedding I think all assignments should be local, and we should have a variable available inside each function, just like arguments, called outer, that's a reference to the function's outer scope. You would use ...
ES5中只有全局作用域和函数作用域,因此var变量声明被提升到了全局作用域,ES6有了块级作用域,let 声明的变量只能在声明的作用域以及其子作用域使用,而var依然只有全局和函数作用域之分。再看下面代码。 1console.log(a)//报错:a is not undefined2let lock =false34if(lock) {5let a = 106}else{7let a ...
August 30, 2016ES6, JavaScriptEdit Post In the last post we learned all about how scoping works with JavaScript let, const and var variables.We now know that var is **function scope**, and now we know that let and const are block scope, which means any time you've got a set of ...
You can also useconstand get the same results, which is what we will talk about in theES6.iovideo. Find an issue with this post? Think you could clarify, update or add something? All my posts are available to edit on Github. Any fix, little or small, is appreciated!
console.log(dataY);//Not available outside function; dataY is undefined Variables can be used before we either declare or initialize them. In this case, the value of the variable will beundefined, but there will not be any runtime error. ...
One of the Javascript's oddities is that you can use variables and functions before they are declared. It's called hoisting. Fortunately, in ES6 let and const variables offer much better behavior. Hoisting Consider the following code: sayHi(); function sayHi() { console.log('Hi there!');...