即使在定义函数之后，也会发生错误，并说未定义函数

Question

在javaScript中调用getSavedTodos（）之后

发生错误，未捕获ReferenceError：未定义getSavedTodos

即使在定义函数getSavedTodos（）之后也会发生错误

我正在使用VS代码

const todos = getSavedTodos()

const filters = {

    search: '',

    hideFalseStates: false

}

const getSavedTodos = function() {

    const todoJSON=localStorage.getItem('todo')

    if(todoJSON !== null) {

        return JSON.parse(todoJSON)

    }

}

不知道错误的发生，代码格式是否有所变化？

Answer 1

您的错误是因为在定义函数之前调用了该函数。该代码是从上到下阅读的，因此在定义它之前，不能使用任何变量或函数。const todos = getSavedTodos() //<-- Move this to after you defined the functionconst filters = {&nbsp; &nbsp; search: '',&nbsp; &nbsp; hideFalseStates: false}const getSavedTodos = function(){&nbsp; &nbsp; const todoJSON = localStorage.getItem('todo')&nbsp; &nbsp; if(todoJSON !== null) {&nbsp; &nbsp; &nbsp; &nbsp; return JSON.parse(todoJSON)&nbsp; &nbsp; }}

Answer 2

在定义它之前，您正在使用它。您有两种选择：在使用之前，只需将定义上移至：const getSavedTodos=function(){&nbsp; &nbsp; const todoJSON=localStorage.getItem('todo')&nbsp; &nbsp; if(todoJSON!==null)&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; return JSON.parse(todoJSON)&nbsp; &nbsp; }}const todos = getSavedTodos()const filters={&nbsp; &nbsp; search: '',&nbsp; &nbsp; hideFalseStates: false}使用函数声明而不是函数表达式，因为它们已被提升（它们在逐步评估代码之前得到评估）：const todos = getSavedTodos()const filters={&nbsp; &nbsp; search: '',&nbsp; &nbsp; hideFalseStates: false}function getSavedTodos(){&nbsp; &nbsp; const todoJSON=localStorage.getItem('todo')&nbsp; &nbsp; if(todoJSON!==null)&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; return JSON.parse(todoJSON)&nbsp; &nbsp; }}