20210520

问题

实现lodash_.get，即链式调用

https://www.lodashjs.com/docs/lodash.get

答案

const obj = {
  a: [{
    b: {
      cd: 0
    }
  }]
}
const v1 = this.test(obj, "a.b.cd", 100);
const v2 = this.test(obj, "a[0].b.cd");
const v3 = this.test(obj, ['a', '0', 'b', 'c']);
const v4 = this.test(obj, ['a', '0', 'b', 'cd']);
const v5 = this.test(obj, 'abc');
const v6 = this.test(obj, 'a');
console.log("path", v1, v2, v3, v4, v5, v6);

test(obj, path, defaultValue) {
  let item = obj;
  let value = defaultValue || 'default';
  // 合成最终数组
  let arr = [];
  if (/\./g.test(path)) {
    path = path.replace(/(\.)(\w+)/g, '[$2]');
    path = path.replace(/^(\w+)(\[)/g,'[$1]$2');
    arr = path.match(/(\w+)/g)
  } else {
    if (Array.isArray(path)) {
      arr = path;
    } else {
      arr = [path];
    }
  }
  for(let i = 0; i < arr.length; i++) {
    if (item[arr[i]] == undefined) {
      break;
    } else {
      item = item[arr[i]];
      if (i == arr.length - 1) {
        value = item;
      }
    }
  }
  return value;
}