javascript - Firebase in react's componentWillMount -


so i'm making firebase + reactjs app, , need check if element exists before components mount, , set state's existing property based on that.

the problem need use 

componentwillmount() {         let newstate = {}         firebase.database()             .ref(`/refs/${this.props.match.params.channel}`)             .once('value', val => val.val())             .then(value => {                 let val = value.val()                 if (val) {                     let dbref = val.ref                     newstate = {                         dbref,                         exists: true                     }                 } else {                     newstate.exists = false                 }                 this.setstate(newstate)             })     }      componentdidmount() {             if(this.state.exists) {                 console.log(`/channels/${this.state.dbref}/messages`)                 firebase.database()                     .ref(`/channels/${this.state.dbref}/messages`)                     .on('value', snap => {                         const snapshot = snap.val()                         let messages = []                         if (snapshot) {                             object.keys(snapshot).foreach(k => messages.push(snapshot[k]))                         }                         this.setstate({ messages })                         this.refs.messages.scrolltop = this.refs.messages.scrollheight                     })     } }

which async, time need access property in componentdidmount firebase query might not have been resolved yet. ideas on how fix it? possible use await in component's functions?

thanks in advance!


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