函數調用獲取請求之前運行的Javascript警報

Question

private isValidURL(url: string) { 
    var isValid = false; 
    this.$http.get(url).then(
     (data) => { 
      console.log('success'); 
      isValid = true; 
     } 
    ).catch( 
     (reason) => { 
      console.log('failure ' + reason); 
      isValid = false; 
     } 
    ).then(
     () => { 
      return isValid; 
     } 
    ) 
} 
private anotherFunc() { 
    if (!this.isValidURL(url)) { 
     alert('Wrong URL'); 
     return false; 
    } 
} 

if語句中的警報在isValidURL的函數調用之前執行。我如何確保函數先執行？

Answer 1

使用承諾。長的版本，巫婆console.log電話是這

private isValidURL(url: string) { 
    return new Promise((resolve, reject) => { 
     this.$http.get(url).then(
      (data) => { 
       console.log('success'); 
       resolve(); 
      } 
     ).catch(
      (reason) => { 
       console.log('failure ' + reason); 
       reject(); 
      } 
     ); 
    } 

private anotherFunc() { 
    this.isValidURL(url).catch(){ 
     alert('Wrong URL'); 
     return false; 
    } 
} 

或短版，只需使用承諾，$http回報

private isValidURL(url: string) { 
    return this.$http.get(url); 
}  
private anotherFunc() { 
    this.isValidURL(url).catch(){ 
     alert('Wrong URL'); 
     return false; 
    } 
} 

Answer 2

不知道有關TS語法，但這樣的：

private isValidURL(url: string) { 
    return this.$http.get(url) 
    .then(() => true,() => false); 
} 
private anotherFunc() { 
    this.isValidURL(url) 
    .then(isValid => { 
     console.log(isValid ? 'Valid' : 'Invalid'); 
    }); 
}