Analyzing the object for interface compatibility

Question

Analyzing the object for interface compatibility

When I receive a query string in one of my REST endpoints using koa-router, each value of the query string object parameter is always a string:

{
  count: "120",
  result: "true",
  text: "ok"
}

Within my codebase, I have an Interface that represents the query string object:

interface Params {
  count: number;
  result: boolean;
  text: string;
}

I aim to convert the query string object so that all values match this interface. What are the best practices for accomplishing this?

javascript typescript

Answer 1

Answer №1

It's unusual to receive numbers and booleans as strings, given that JSON allows unquoted values for both numeric and boolean data types.

The JSON.parse() method includes an optional reviver callback parameter, which you can utilize within a request interceptor to standardize string representations of numbers and booleans before they reach your interface.

const data = `{
  "count": "120",
  "resut": "false",
  "text": "ok"
}`

const reviver = (key, value) => {
   if(typeof value === 'string' && !isNaN(value)){
       return Number(value)
   }else if(value === 'true' || value === 'false'){
       return value === 'true' ? true : false;
   }   
   return value;
}

console.log(JSON.parse(data, reviver ))

Answer 2

It's unusual to receive numbers and booleans as strings, given that JSON allows unquoted values for both numeric and boolean data types.

The JSON.parse() method includes an optional reviver callback parameter, which you can utilize within a request interceptor to standardize string representations of numbers and booleans before they reach your interface.

const data = `{
  "count": "120",
  "resut": "false",
  "text": "ok"
}`

const reviver = (key, value) => {
   if(typeof value === 'string' && !isNaN(value)){
       return Number(value)
   }else if(value === 'true' || value === 'false'){
       return value === 'true' ? true : false;
   }   
   return value;
}

console.log(JSON.parse(data, reviver ))

Answer 3

Answer №2

To ensure the input aligns with the expected interface, it is important to convert each property to the correct type.

function convertInputToParams(input:any) : Params {
    var obj = typeof input === "string" 
            ? JSON.parse(input) 
            : input;
    obj.count = +obj.count;
    obj.result = obj.result === "true" ? true : false;
    return obj as Params;
}

An alternative approach would be to create a default instance of Params with predefined properties, then iterate over them to verify that each property in the converted object matches the expected type.

function convertInputToInterface(example:any, input:any) {
    Object.keys(example).forEach(function(key,index) {
        if (!input[key]) return;
        let exampleType = typeof example[key];
        let inputType = typeof input[key];
        if (exampleType !== inputType) {
            if (exampleType == "string") input[key] = input[key] + "";
            if (exampleType == "number") input[key] = +input[key];
            if (exampleType == "boolean") input[key] = input[key] === "true" ? true : false;
            // Handle other cases as needed
        }
    });
    return input;
}

Answer 4

To ensure the input aligns with the expected interface, it is important to convert each property to the correct type.

function convertInputToParams(input:any) : Params {
    var obj = typeof input === "string" 
            ? JSON.parse(input) 
            : input;
    obj.count = +obj.count;
    obj.result = obj.result === "true" ? true : false;
    return obj as Params;
}

An alternative approach would be to create a default instance of Params with predefined properties, then iterate over them to verify that each property in the converted object matches the expected type.

function convertInputToInterface(example:any, input:any) {
    Object.keys(example).forEach(function(key,index) {
        if (!input[key]) return;
        let exampleType = typeof example[key];
        let inputType = typeof input[key];
        if (exampleType !== inputType) {
            if (exampleType == "string") input[key] = input[key] + "";
            if (exampleType == "number") input[key] = +input[key];
            if (exampleType == "boolean") input[key] = input[key] === "true" ? true : false;
            // Handle other cases as needed
        }
    });
    return input;
}

Analyzing the object for interface compatibility

Answer №1

Answer №2

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