JAVASCRIPT extractKey.js

import valueToKey from "./valueToKey.js";
// http://www.w3.org/TR/2015/REC-IndexedDB-20150108/#dfn-steps-for-extracting-a-key-from-a-value-using-a-key-path
const extractKey = (keyPath, value) => {
  if (Array.isArray(keyPath)) {
    const result = [];
    for (let item of keyPath) {
      // This doesn't make sense to me based on the spec, but it is needed to pass the W3C KeyPath tests (see same
      // comment in validateKeyPath)
      if (item !== undefined && item !== null && typeof item !== "string" && item.toString) {
        item = item.toString();
      }
      const key = extractKey(item, value).key;
      result.push(valueToKey(key));
    }
    return {
      type: "found",
      key: result
    };
  }
  if (keyPath === "") {
    return {
      type: "found",
      key: value
    };
  }
  let remainingKeyPath = keyPath;
  let object = value;
  while (remainingKeyPath !== null) {
    let identifier;
    const i = remainingKeyPath.indexOf(".");
    if (i >= 0) {
      identifier = remainingKeyPath.slice(0, i);
      remainingKeyPath = remainingKeyPath.slice(i + 1);
    } else {
      identifier = remainingKeyPath;
      remainingKeyPath = null;
    }

    // special cases: https://w3c.github.io/IndexedDB/#evaluate-a-key-path-on-a-value
    const isSpecialIdentifier = identifier === "length" && (typeof object === "string" || Array.isArray(object)) || (identifier === "size" || identifier === "type") && typeof Blob !== "undefined" && object instanceof Blob || (identifier === "name" || identifier === "lastModified") && typeof File !== "undefined" && object instanceof File;
    if (!isSpecialIdentifier && (typeof object !== "object" || object === null || !Object.hasOwn(object, identifier))) {
      return {
        type: "notFound"
      };
    }
    object = object[identifier];
  }
  return {
    type: "found",
    key: object
  };
};
export default extractKey;