方法鏈返回undefined

Question

我有以下的JavaScript類

var a = function() { 
    this.data = {}; 
}; 

a.prototype.parseString = function (string) { 
    this.data = string.split(','); 
} 

a.prototype.performOperationB = function() { 
    this.iPo = _.map(this.data, function() { 
     if (item.indexOf('ip') > -1) { 
      return item; 
     } 
    }); 
} 

a.prototype.save = function (string) { 
    this.parseString(string) 
     .performOperationB() 
     // some other chained methods 
} 
var b = new a(); 

b.save(string); 

將陸續內的另一個方法返回TypeError: Cannot read property 'performOperationB' of undefined

是否有可能鏈原型方法之一？

Answer 1

返回this從

a.prototype.parseString = function(string) { 
    this.data = string.split(','); 
    return this; 
} 

因爲現在方法返回undefined

var a = function() { 
 
    this.data = {}; 
 
}; 
 

 
a.prototype.parseString = function (string) { 
 
    this.data = string.split(','); 
 
    return this; 
 
} 
 

 
a.prototype.performOperationB = function() { 
 
    this.iPo = _.map(this.data, function (item) { 
 
    if (item.indexOf('ip') > -1) { 
 
     return item; 
 
    } 
 
    }); 
 
} 
 

 
a.prototype.save = function (string) { 
 
    this.parseString(string) 
 
    .performOperationB() 
 
} 
 
var b = new a(); 
 

 
b.save('string');

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