将父范围添加到匿名函数 - JavaScript到Angular 2

Question

我试图在Angular 2项目中包含一个旧的JavaScript模块，我遇到了访问父范围的问题。

let testString = "Parent Scope Accessed!";

Object.keys(data).forEach((function(Key, Index) {
    if(filter.type == 'parameter') {
      Object.keys(dirArray).forEach(function(dirKey, dirIndex) {
        linkArray = dirArray[dirKey];
        if(filter.dir == 2) {  //Direction filter
          Object.keys(linkArray).forEach(function(linkKey, linkIndex) {
            if(filter.type != 'sub')) {
              dataObject = linkArray[linkKey];

              //ERROR with scoping occurs below.  Need to add parent scope.
              console.log(this.testString);
            }
          });
        }
      });
    }
}));

我试过这样的事情：

let testString = "Parent Scope Accessed!";

Object.keys(data).forEach((function(Key, Index) => {
    if(filter.type == 'parameter') {
      Object.keys(dirArray).forEach(function(dirKey, dirIndex) => {
        linkArray = dirArray[dirKey];
        if(filter.dir == 2) {  //Direction filter
          Object.keys(linkArray).forEach(function(linkKey, linkIndex) => {
            if(filter.type != 'sub')) {
              dataObject = linkArray[linkKey];

              //ERROR with scoping occurs below.  Need to add parent scope.
              console.log(this.testString);
            }
          });
        }
      });
    }
}));

但是这会产生一系列全新的问题，但至少IDE会指出已添加了父范围。我假设我没有使用'=＆gt;'语法正确。有更好的方法吗？

Answer 1

删除function字，并在定义函数时使用胖箭头=>

 let testString = "Parent Scope Accessed!";

Object.keys(data).forEach(((Key, Index)=> {
    if(filter.type == 'parameter') {
      Object.keys(dirArray).forEach((dirKey, dirIndex)=> {
        linkArray = dirArray[dirKey];
        if(filter.dir == 2) {  //Direction filter
          Object.keys(linkArray).forEach((linkKey, linkIndex)=> {
            if(filter.type != 'sub')) {
              dataObject = linkArray[linkKey];

              //ERROR with scoping occurs below.  Need to add parent scope.
              console.log(this.testString);
            }
          });
        }
      });
    }
}));

或

在变量中定义根this（在本例中为var that）：

var that = this;
let testString = "Parent Scope Accessed!";

Object.keys(data).forEach((function(Key, Index) => {
    if(filter.type == 'parameter') {
      Object.keys(dirArray).forEach(function(dirKey, dirIndex) => {
        linkArray = dirArray[dirKey];
        if(filter.dir == 2) {  //Direction filter
          Object.keys(linkArray).forEach(function(linkKey, linkIndex) => {
            if(filter.type != 'sub')) {
              dataObject = linkArray[linkKey];

              //ERROR with scoping occurs below.  Need to add parent scope.
              console.log(that.testString); //Use that instead of this here to refer to the parent scope
            }
          });
        }
      });
    }
}));