es6 变量和作用域的问题

Question

先举个例子说：const testFun = () => {

let testParams
const sonFun = () => {
    testParams = 3
}
console.log(testParams)

}
像上面这样的写法，我怎么才能console出testParams的值呢？

Answer 1

首先你得先执行了sonFun这个方法，你才能给testParams赋上值

Answer 2

你这赋值根本就没执行嘛

let testParams
const sonFun = () => {
    testParams = 3
}
sonFun()
console.log(testParams)

Answer 3

const testFun = () => {
        let testParams
        const sonFun = () => {
            testParams = 3
        }
        sonFun()
        console.log(testParams)
    }
    testFun()

Answer 4

let testParams
const sonFun = () => {
    testParams = 3
}
sonFun();
console.log(testParams)

这个箭头函数的作用域，在这段代码里面怕是没有提现出来