我在单击按钮时调用了 handleSelection 方法，但是，如果我单击该按钮，当它到达 this.setState({selectedFoods:新选择});。该方法中的所有其他内容都正确执行(正如我的各种 console.logs 告诉我的:))。第二次单击该按钮时，该方法中的所有内容都会再次执行，并且 setState 起作用。

var Flavor = React.createClass({
  getInitialState: function() {
    return { foods: {}, selectedFoods: [], affinities: [] };
  },
        componentDidMount: function() {
            $.ajax({
              url: this.props.url,
              dataType: 'json',
              cache: false,
              success: function(data) {
                this.setState({foods: data});
              }.bind(this),
              error: function(xhr, status, err) {
                console.error(this.props.url, status, err.toString());
              }.bind(this)
            });
          },
  componentDidUpdate: function () {
    $('#select-food').selectize({
      onChange: this.handleSelection
      }
    );
  },
  handleSelection: function (e) {
    if (e.target) {
      var selectedFood = e.target.id;
    } else {
      var selectedFood = e;
    }
    console.log(selectedFood);

    if (this.state.foods[selectedFood]) {
      var selections = this.state.selectedFoods;
      var newSelections = selections.concat(selectedFood);
      console.log("newSelections: "+newSelections)
      var state = Object.assign(this.state, {selectedFoods: newSelections});
      this.setState(state);
      console.log("state: "+this.state.selectedFoods)
      this.handleAffinities();
    } else {
      console.log("** "+selectedFood+" **");
    }

  },
  handleAffinities: function() {

    console.log("selectedFoods: "+this.state.selectedFoods.length)
    if (this.state.selectedFoods.length > 0) {
      var allAffinities = this.state.selectedFoods.map((food) => {
        return this.state.foods[food];
      });
      console.log(allAffinities.length);
      console.log(allAffinities);

      var commonAffinities = allAffinities[0];

      allAffinities.forEach((affinities) => {
        commonAffinities = commonAffinities.filter((n) => {
          return affinities.indexOf(n) != -1;
        });
      })

      this.setState({affinities: commonAffinities});
    } else {
      this.setState({ affinities: [] });
    }

  },
  handleRemove: function(food) {
    var selectedFoods = this.state.selectedFoods;
    var index = selectedFoods.indexOf(food);
    var updatedSelection = selectedFoods.splice(index, 1);
    this.setState({selectedFoods: selectedFoods});
    this.handleAffinities();
  },

为什么除了我的 setState 函数，所有的东西第一次都能正确执行？为什么它在第二次点击时起作用？

最佳答案

状态正在按照预期的方式发生变化。问题在于，在您调用 setState 之后，您的 console.log 语句在设置新状态之前立即触发。

来自docs :

setState() does not immediately mutate this.state but creates a pending state transition. Accessing this.state after calling this method can potentially return the existing value.

如果您想在状态转换完成后触发 console.log 语句，请将函数作为回调传递给 setState()。

this.setState({selectedFoods: newSelections}, () => {
    console.log(this.state.selectedFoods);
});

关于javascript - React setState 在第一次尝试时不起作用，但在第二次尝试时起作用？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/37847028/