set.ts

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decodeToken.ts dereference.ts encodeToken.ts get.ts index.ts isPointer.ts set.ts

set.ts

import * as has from 'lodash.has';
import { isPointer, decodeToken } from './index';
import { SetPointer } from './types';

export const set: SetPointer = (obj, pointer, value) => {

¶

A JSON pointer must begin with the symbols ‘#’, ‘/‘ or be an empty string ‘’. So as a first step, we check that this assumption is true and bail if not.
```
  if (!isPointer(pointer)) {
    throw new Error(`invalid JSON pointer specified: '${pointer}'`);
  }
```
¶

If this check passes we have a valid pointer. In order to dereference its value, we will split the pointer into its orthogonal pieces and then iterate schema checking from left to right that each piece of pointer references a valid path in schema.
```
  const fragments = pointer.split('/');
  let ref = obj;
  return fragments.forEach((fragment, index) => {
```

If fragment points to the root path of object we can just return the object itself.

    if (fragment === '#' || fragment === '/' || fragment === '') {
      return;
    }

¶

Here we decode fragment according to the JSON pointer specification, replacing the character codes ‘~1’ and ‘~0’ with the symbols ‘/‘ and ‘~’ respectively.
```
    const token = decodeToken(fragment);
```

If the ‘object’ is array assume that token indicates an index in this array and try to resolve it appropriately.

    if (Array.isArray(ref)) {
      const i = parseInt(token, 10);

      if (!ref.indexOf(i)) {
        throw new Error(
          `could not set JSON pointer: ${pointer}. Array does not have`
          + ` index: ${index}::${JSON.stringify(obj)}`);
      }

      if ((index + 1) === fragments.length) {
        ref[i] = value;
        return;
      }

      ref = ref[i];

Otherwise if object is not an Array we expect object to be of type Object and that token references a valid path in object.

    } else {
      if (!has(ref, token)) {
        throw new Error(
          `could not set pointer: '${pointer}'. The fragment ${token}`
          + ` is not a valid property of object: ${JSON.stringify(obj, null, 2)}`);
      }

      if ((index + 1) === fragments.length) {
        ref[token] = value;
        return;
      }
      ref = ref[token];
    }
  });
};