javascript - 如何避免在for循环完成之前调用.map函数？

Question

我有一个函数handleForm(formData):

    handleFormData(formData) {
    const { school, schoolyear } = this.props.params;
    const { addDataToBackend } = this.props;
    const { selectedDate } = this.props.schoolVacationDelivery;

    if (!_.isEmpty(selectedDate)) {
        var structuredFormData = [];
        for (var key in formData) {
            var prefix = key.split("=")[0];
            var appendix = key.split("=")[1];
            var dataObject = structuredFormData.find(o => o.season === prefix);
            if (!dataObject) {
                dataObject = { season: prefix };
                structuredFormData.push(dataObject);
            }
            dataObject[appendix] = formData[key];
        }

        let updatedStructuredFormData = structuredFormData.map(x => {
            let season = x.season;
            x.date = selectedDate.find(e => e.indexOf(season) > -1).split("=")[1];
            return x;
        });

        addDataToBackend(schoolyear, updatedStructuredFormData);
    } else {
        addDataToBackend(schoolyear, []);
    }

    browserHistory.push(
        `/schooladmin/home/school/${school}/schoolyear/${schoolyear}/prepackaged`
    );
}

有时我会在这一行得到Cannot read property 'split' of undefined x.date = selectedDate.find(e => e.indexOf(season) > -1 ).split("=")[1];。我如何确保在 for 循环完成之前不会调用 structuralFormData.map ？我如何更改代码，以便始终确保 for 循环在调用 structuralFormData.map 函数之前结束？

这是错误输出:

第 98 行:let UpdatedStructuredFormData = StructuredFormData.map(x => { ..

第 100 行:x.date = selectedDate.find(e => e.indexOf(season) > -1).split("=")[1];

Answer 1

您的 for 循环不包含任何异步操作(例如 API 请求、setTimeout、promise 等)，因此 JavaScript 始终会在 .map.

看来您的问题不在 handleFormData 函数之外(例如，您在函数内部使用的 props 中的数据)。

检查您如何获取此数据，并在需要时再次寻求帮助。祝你好运!