JSON Stringify with number as decimal float value

stringify-with-floats.ts

const beginFloat = "~begin~float~";
const endFloat = "~end~float~";

type Config = Record<string, "float">;

export const stringifyWithFloats =
  (config: Config = {}, decimals = 2) =>
  (
    inputValue: Record<string, any>,
    inputReplacer?: (this: any, key: string, value: any) => any,
    space?: string | number
  ) => {
    const inputReplacerIsFunction = typeof inputReplacer === "function";
    let isFirstIteration = true;
    const jsonReplacer = (key: string, val: any) => {
      if (isFirstIteration) {
        isFirstIteration = false;
        return inputReplacerIsFunction ? inputReplacer(key, val) : val;
      }
      let value: any;
      if (inputReplacerIsFunction) {
        value = inputReplacer(key, val);
      } else if (Array.isArray(inputReplacer)) {
        // remove the property if it is not included in the inputReplacer array
        value = (inputReplacer as any).indexOf(key) !== -1 ? val : undefined;
      } else {
        value = val;
      }
      const forceFloat =
        config[key] === "float" &&
        (value || value === 0) &&
        typeof value === "number" &&
        !value.toString().toLowerCase().includes("e");
      return forceFloat ? `${beginFloat}${value}${endFloat}` : value;
    };
    const json = JSON.stringify(inputValue, jsonReplacer, space);
    const regexReplacer = (match: string, num: any) => {
      return num.includes(".") || Number.isNaN(num)
        ? Number.isNaN(num)
          ? num
          : Number(num).toFixed(decimals)
        : `${num}.${"0".repeat(decimals)}`;
    };
    const re = new RegExp(`"${beginFloat}(.+?)${endFloat}"`, "g");
    return json.replace(re, regexReplacer);
  };

usage.ts

// Example usage
import fetch from "node-fetch";
import {stringifyWithFloats} from "./stringify-with-floats";

async function bootstrap() {
  try {
    const body = {
      title: "Test SKU",
      siteId: "_____",
      externalId: "test_package",
      type: "subscription",
      price: [
        {
          offset: "0d",
          amount: 50, // Formats to 50 in JS, 50.00 in stringifyWithFloats()
          currency: "USD",
          repeat: false,
        },
        {
          offset: "30d",
          amount: 50, // Formats to 50 in JS, 50.00 in stringifyWithFloats()
          currency: "USD",
          repeat: true,
        },
      ],
    };

    const bodyWithFloats = stringifyWithFloats({
      amount: "float", // Target amount key in provided object.
    })(body);

    const response = await fetch("https://api.example.com/sku", {
      method: "POST",
      headers: {
        Authorization: "________",
        "Content-Type": "application/json",
      },
      body: bodyWithFloats,
    });

    if (!response.ok) {
      throw new Error(response.statusText);
    }

    const json = await response.json();
    console.log(json);
  } catch (error) {
    console.log(error);
  }
}
bootstrap();