遺漏的類型錯誤：無法讀取的不確定

Question

財產「狀態」我有以下功能：

extractCountries: function() { 
    var newCountries = []; 
    _.forEach(this.props.countries, function(country) { 

     var monthTemp = Utils.thisMonthTemp(parseFloat(country["name"]["temperature"])); 

     if(parseFloat(country["name"]["safety"]) > this.state.minSafety && 
      parseFloat(country["name"]["nature"]) > this.state.minNature && 
      this.state.weather.min <= monthTemp && 
      monthTemp <= this.state.weather.max) { 

      newCountries.push(country); 
     } 
    }).bind(this); 
    return newCountries; 
    } 

上線parseFloat(country["name"]["safety"]) > this.state.minSafety &&我得到：

Uncaught TypeError: Cannot read property 'state' of undefined

但我結合外部陣營object：

}).bind(this); 

那麼爲什麼會出現這種錯誤呢？

Answer 1

試試這個

extractCountries: function() { 
     var newCountries = []; 
     _.forEach(this.props.countries, function(country) { 

      var monthTemp = Utils.thisMonthTemp(parseFloat(country["name"]["temperature"])); 

      if(parseFloat(country["name"]["safety"]) > this.state.minSafety && 
       parseFloat(country["name"]["nature"]) > this.state.minNature && 
       this.state.weather.min <= monthTemp && 
       monthTemp <= this.state.weather.max) { 

       newCountries.push(country); 
      } 
     }, this); 
     return newCountries; 
     } 

Answer 2

正如評論提到你只需要做到這一點

extractCountries: function() { 
    var newCountries = []; 
    _.forEach(this.props.countries, function(country) { 

     var monthTemp = Utils.thisMonthTemp(parseFloat(country["name"]["temperature"])); 

     if(parseFloat(country["name"]["safety"]) > this.state.minSafety && 
      parseFloat(country["name"]["nature"]) > this.state.minNature && 
      this.state.weather.min <= monthTemp && 
      monthTemp <= this.state.weather.max) { 

      newCountries.push(country); 
     } 
    }.bind(this)); 
    return newCountries; 
    }