Version of JSON.stringify limitied to a specific depth.

stringify.js

// Similar to JSON.stringify but limited to a specified depth (default 1)
// The approach is to prune the object first, then just call JSON.stringify to do the formatting

const prune = (obj, depth = 1) => {
  if (Array.isArray(obj) && obj.length > 0) {
    return (depth === 0) ? ['???'] : obj.map(e => prune(e, depth - 1))
  } else if (obj && typeof obj === 'object' && Object.keys(obj).length > 0) {
    return (depth === 0) ? {'???':''} : Object.keys(obj).reduce((acc, key) => ({ ...acc, [key]: prune(obj[key], depth - 1)}), {})
  } else {
    return obj
  }
}

const stringify = (obj, depth = 1, space) => JSON.stringify(prune(obj, depth), null, space)

const stringify = (obj: any, depth = 1): string => {
  return !obj
    ? JSON.stringify(obj, null, 2)
    : typeof obj === 'object'
    ? JSON.stringify(
        JSON.parse(
          depth < 1
            ? '"???"'
            : `{${Object.keys(obj)
                .map((k) => `"${k}": ${stringify(obj[k], depth - 1)}`)
                .join(', ')}}`,
        ),
        null,
        2,
      )
    : JSON.stringify(obj, null, 2);
};

working with null, 2 format in typescript

Thanks for the update! I actually wrote it to use in the browser console, so can't really use TS. But your more modern code is much better (and your bug fix) :-)

I have completely changed it now anyway: I decided that I should just create a clone of the object, pruned to the right depth; and then just call JSON.stringify to do the formatting.

Thank you @bennettmcelwee and @sturmenta. I've adapted sturmenta's code back into native js, cleaned it up a bit, and added handling for undefined. Should be fairly efficient and robust now, as well as being easily adjusted to needs.

function stringifyMaxDepth (obj, depth = 1) {
    // recursion limited by depth arg
    if (!obj || typeof obj !== 'object') return JSON.stringify(obj)

    let curDepthResult = '"<?>"' // too deep
    if (depth > 0) {
        curDepthResult = Object.keys(obj)
            .map( (key) => {
                let val = stringifyMaxDepth(obj[key], depth - 1)
                if (val === undefined) val = 'null'
                return `"${key}": ${val}`
            })
            .join(', ')
        curDepthResult = `{${curDepthResult}}`
    }

    return JSON.stringify(JSON.parse(curDepthResult))
}