为什么我的功能无法识别其他功能？

Question

Why do I get the error: Uncaught ReferenceError: writeUserData is not defined(…)

or the other error when i include this.writeUserData which is: Cannot read property 'writeUserData' of undefined

The function still posts the correct data to firebase so why is it complaining? and more so what is the correct way to call a function inside another function. i thought this was the right way to do it?

signUserUp(){
    let name = this.state.nameValue;
    let slackName = this.state.slackNameValue;
    let email = this.state.emailValue;
    let password = this.state.passwordValue;
    firebase.auth().createUserWithEmailAndPassword(email, password).then(
      function(result){
        writeUserData(name, result.uid, email, slackName);
      },
      function(error){
        let errorCode = error.code;
        let errorMessage = error.message;
        console.log(errorMessage, '***');
        console.log(errorCode, 'code');
        });
    };

    writeUserData(name, useruid, email, slackName){
      firebase.database().ref('/pairs/' + useruid).set({
        name: name,
        useruid: useruid,
        email: email,
        slackName: slackName
      });
    }

EDIT: This code is inside a React component using ES6 syntax...

Answer 1

Your just need to declare it as a function:

function writeUserData(name, useruid, email, slackName){...};

You think that it succeeds only because createUserWithEmailAndPassword() creates your user, and only after that calls the success handler.

But this is actually never executed in your case:

firebase.database().ref('/pairs/' + useruid).set

Answer 2

For you first question: The reason is that you didn't declare writeUserData as a function.

Here is a way similar to Alexey Soshin's answer, but with an alternative syntax.

 var signUserUp = function() { let name = this.state.nameValue; let slackName = this.state.slackNameValue; let email = this.state.emailValue; let password = this.state.passwordValue; firebase.auth().createUserWithEmailAndPassword(email, password).then( function(result){ writeUserData(name, result.uid, email, slackName); }, function(error){ let errorCode = error.code; let errorMessage = error.message; console.log(errorMessage, '***'); console.log(errorCode, 'code'); }); }; var writeUserData = function (name, useruid, email, slackName) { firebase.database().ref('/pairs/' + useruid).set({ name: name, useruid: useruid, email: email, slackName: slackName }); } 

For your second question ("...when I include this.writeUserData ... Cannot read property 'writeUserData' of undefined "): In this case this is undefined.

To define this for your second question, you'd have to define your writeUserData inside this .

To define writeUserData inside this :

1. add it on the prototype of the parent function

    signUserUp.prototype.writeUserData = function(name, useruid, email, slackName) { ... } 

2. bind the this of the parent function to the child function

    firebase.auth().createUserWithEmailAndPassword(email, password).then( ... ).bind(this); 

3. bind the this of the child function to your function

    function(result) { ... }.bind(this), 

... which is awkward. So do it the first way! :)

 var signUserUp = function() { let name = this.state.nameValue; let slackName = this.state.slackNameValue; let email = this.state.emailValue; let password = this.state.passwordValue; signUserUp.prototype.writeUserData = function(name, useruid, email, slackName) { firebase.database().ref('/pairs/' + useruid).set({ name: name, useruid: useruid, email: email, slackName: slackName }); } firebase.auth().createUserWithEmailAndPassword(email, password).then( function(result) { this.writeUserData(name, result.uid, email, slackName); }.bind(this), function(error) { let errorCode = error.code; let errorMessage = error.message; console.log(errorMessage, '***'); console.log(errorCode, 'code'); }).bind(this); };