I'm new to TypeScript. Below is my code with errors mentioned in comments. What is going wrong?

type BooleanAttributeName = string;
type PairedAttribute = {
    [_: string]: string | number;
};
type CompositeAttribute = [
    PairedAttribute,
    BooleanAttributeName | BooleanAttributeName[]
];
type Attributes = CompositeAttribute | PairedAttribute;

function SetAttributes(attributes: Attributes) {
    if (attributes.length === undefined) {
        for (const key in attributes) {
            console.log(key, attributes[key]); /*Error: Element implicitly has an 'any' type because expression of type 'string' can't be used to index type 'Attributes'. No index signature with a parameter of type 'string' was found on type 'Attributes'.*/
        }
    }
    attributes.map((item) => { /*This expression is not callable. Not all constituents of type 'string | number | (<U>(callbackfn: (value: string | PairedAttribute | string[], index: number, array: (string | PairedAttribute | string[])[]) => U, thisArg?: any) => U[])' are callable. Type 'string' has no call signatures.*/ /*Parameter 'item' implicitly has an 'any' type.*/
        if (item.length === undefined) {
            for (const key in item) {
                console.log(key, item[key]);
            }
        } else if (typeof item === "object") {
            item.map((BooleanAttributeName) => { /*Parameter 'BooleanAttributeName' implicitly has an 'any' type.*/
                console.log(BooleanAttributeName);
            });
        } else {
            console.log(item);
        }
    });
}

let sample: Attributes = [
    {
        key1: "value1",
        key2: "value2",
    },
    ["BooleanAttribute1", "BooleanAttribute2"],
];

SetAttributes(sample);

I tried to use some concepts of narrowing from the official TypeScript docs but still I am facing these problems.

I want to know what can be solution for the problem.

Try to add some type casting and checking:

type BooleanAttributeName = string;
type PairedAttribute = {
  [_: string]: string | number;
};
type CompositeAttribute = [
  PairedAttribute,
  BooleanAttributeName | BooleanAttributeName[]
];
type Attributes = CompositeAttribute | PairedAttribute;

function SetAttributes(attributes: Attributes) {
  if (typeof attributes === 'object') {
    const attr = attributes as PairedAttribute;
    for (const key in attr) {
      console.log(key, attr[key]); 
    }
  }
  if (attributes instanceof Array) {
    const attr = attributes as CompositeAttribute;
    attr.map((item) => {
      if (typeof item === "object") {
        const it = item as PairedAttribute;
        for (const key in it) {
          console.log(key, it[key]);
        }
      } else {
        console.log(item);
      }
    });
  }
}

let sample: Attributes = [
  {
    key1: "value1",
    key2: "value2",
  },
  ["BooleanAttribute1", "BooleanAttribute2"],
];

SetAttributes(sample);

Link to playground