javascript - 未捕获的类型错误 : Cannot read property 'state' of undefined

Question

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;
  }

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

未捕获的类型错误:无法读取未定义的属性“状态”

但我正在绑定(bind)外部 React 对象:

}).bind(this);

那么为什么会出现这个错误呢？

Answer 1

试试这个

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;
      }