feat: Add extract method

.eslintrc.json

@@ -1,10 +1,11 @@
 {
-  "plugins": ["jsdoc"],
+  "plugins": ["jsdoc", "expect-type"],
   "extends": [
     "eslint:recommended",
     "plugin:jsdoc/recommended",
     "plugin:n/recommended",
     "plugin:unicorn/recommended",
+    "plugin:expect-type/recommended",
     "prettier"
   ],
   "env": { "node": true },

package.json

@@ -79,6 +79,7 @@
     "benchmark": "^2.1.4",
     "eslint": "^8.29.0",
     "eslint-config-prettier": "^8.5.0",
+    "eslint-plugin-expect-type": "^0.2.1",
     "eslint-plugin-jest": "^27.1.6",
     "eslint-plugin-jsdoc": "^39.6.4",
     "eslint-plugin-n": "^15.6.0",

src/api/extract.spec.ts

@@ -0,0 +1,120 @@
+import * as fixtures from '../__fixtures__/fixtures.js';
+import cheerio from '..';
+
+interface RedSelObject {
+  red: string | undefined;
+  sel: string | undefined;
+}
+
+interface RedSelMultipleObject {
+  red: string[];
+  sel: string[];
+}
+
+describe('$.extract', () => {
+  it('() : should extract values for selectors', () => {
+    const $ = cheerio.load(fixtures.eleven);
+    const $root = cheerio.load(fixtures.eleven).root();
+    // An empty object should lead to an empty extraction.
+
+    // $ExpectType ExtractedMap<{}>
+    const emptyExtract = $root.extract({});
+    expect(emptyExtract).toStrictEqual({});
+    // Non-existent values should be undefined.
+
+    // $ExpectType ExtractedMap<{ foo: string; }>
+    const simpleExtract = $root.extract({ foo: 'bar' });
+    expect(simpleExtract).toStrictEqual({ foo: undefined });
+
+    // Existing values should be extracted.
+    expect<{ red: string | undefined }>(
+      $root.extract({ red: '.red' })
+    ).toStrictEqual({
+      red: 'Four',
+    });
+    expect<RedSelObject>(
+      $root.extract({ red: '.red', sel: '.sel' })
+    ).toStrictEqual({
+      red: 'Four',
+      sel: 'Three',
+    });
+    // Descriptors for extractions should be supported
+    expect<RedSelObject>(
+      $root.extract({
+        red: { selector: '.red' },
+        sel: { selector: '.sel' },
+      })
+    ).toStrictEqual({ red: 'Four', sel: 'Three' });
+    // Should support extraction of multiple values.
+
+    // $ExpectType ExtractedMap<{ red: [string]; sel: [string]; }>
+    const multipleExtract = $root.extract({
+      red: ['.red'],
+      sel: ['.sel'],
+    });
+    expect<RedSelMultipleObject>(multipleExtract).toStrictEqual({
+      red: ['Four', 'Five', 'Nine'],
+      sel: ['Three', 'Nine', 'Eleven'],
+    });
+    // Should support custom `prop`s.
+    expect<RedSelObject>(
+      $root.extract({
+        red: { selector: '.red', value: 'outerHTML' },
+        sel: { selector: '.sel', value: 'tagName' },
+      })
+    ).toStrictEqual({ red: '<li class="red">Four</li>', sel: 'LI' });
+    // Should support custom `prop`s for multiple values.
+    expect<{ red: string[] }>(
+      $root.extract({
+        red: [{ selector: '.red', value: 'outerHTML' }],
+      })
+    ).toStrictEqual({
+      red: [
+        '<li class="red">Four</li>',
+        '<li class="red">Five</li>',
+        '<li class="red sel">Nine</li>',
+      ],
+    });
+    // Should support custom extraction functions.
+    expect<{ red: string | undefined }>(
+      $root.extract({
+        red: {
+          selector: '.red',
+          value: (el, key) => `${key}=${$(el).text()}`,
+        },
+      })
+    ).toStrictEqual({ red: 'red=Four' });
+    // Should support custom extraction functions for multiple values.
+    expect<{ red: string[] }>(
+      $root.extract({
+        red: [
+          {
+            selector: '.red',
+            value: (el, key) => `${key}=${$(el).text()}`,
+          },
+        ],
+      })
+    ).toStrictEqual({ red: ['red=Four', 'red=Five', 'red=Nine'] });
+    // Should support extraction objects
+
+    // $ExpectType ExtractedMap<{ section: { selector: string; value: { red: string; sel: string; }; }; }>
+    const subExtractObject = $root.extract({
+      section: {
+        selector: 'ul:nth(1)',
+        value: {
+          red: '.red',
+          sel: '.blue',
+        },
+      },
+    });
+
+    expect<{ section: RedSelObject | undefined }>(
+      subExtractObject
+    ).toStrictEqual({
+      section: {
+        red: 'Five',
+        sel: 'Seven',
+      },
+    });
+  });
+});

src/api/extract.ts

@@ -0,0 +1,92 @@
+import type { AnyNode, Element } from 'domhandler';
+import type { Cheerio } from '../cheerio.js';
+import type { prop } from './attributes.js';
+
+type ExtractDescriptorFn = (
+  el: Element,
+  key: string,
+  // TODO: This could be typed with ExtractedMap
+  obj: Record<string, unknown>
+) => unknown;
+
+interface ExtractDescriptor {
+  selector: string;
+  value?: string | ExtractDescriptorFn | ExtractMap;
+}
+
+type ExtractValue = string | ExtractDescriptor | [string | ExtractDescriptor];
+
+export interface ExtractMap {
+  [key: string]: ExtractValue;
+}
+
+type ExtractedValue<V extends ExtractValue, M extends ExtractMap> = V extends [
+  string | ExtractDescriptor
+]
+  ? NonNullable<ExtractedValue<V[0], M>>[]
+  : V extends string
+  ? string | undefined
+  : V extends ExtractDescriptor
+  ? V['value'] extends ExtractMap
+    ? ExtractedMap<V['value']> | undefined
+    : V['value'] extends ExtractDescriptorFn
+    ? ReturnType<V['value']> | undefined
+    : ReturnType<typeof prop> | undefined
+  : never;
+
+export type ExtractedMap<M extends ExtractMap> = {
+  [key in keyof M]: ExtractedValue<M[key], M>;
+};
+
+function getExtractDescr(
+  descr: string | ExtractDescriptor
+): Required<ExtractDescriptor> {
+  if (typeof descr === 'string') {
+    return { selector: descr, value: 'textContent' };
+  }
+
+  return {
+    selector: descr.selector,
+    value: descr.value ?? 'textContent',
+  };
+}
+
+/**
+ * Extract multiple values from a document, and store them in an object.
+ *
+ * @param map - An object containing key-value pairs. The keys are the names of
+ *   the properties to be created on the object, and the values are the
+ *   selectors to be used to extract the values.
+ * @returns An object containing the extracted values.
+ */
+export function extract<M extends ExtractMap, T extends AnyNode>(
+  this: Cheerio<T>,
+  map: M
+): ExtractedMap<M> {
+  const ret: Record<string, unknown> = {};
+
+  for (const key in map) {
+    const descr = map[key];
+    const isArray = Array.isArray(descr);
+
+    const { selector, value } = getExtractDescr(isArray ? descr[0] : descr);
+
+    const fn: ExtractDescriptorFn =
+      typeof value === 'function'
+        ? value
+        : typeof value === 'string'
+        ? (el: Element) => this._make(el).prop(value)
+        : (el: Element) => this._make(el).extract(value);
+
+    if (isArray) {
+      ret[key] = this._findBySelector(selector, Number.POSITIVE_INFINITY)
+        .map((_, el) => fn(el, key, ret))
+        .get();
+    } else {
+      const $ = this._findBySelector(selector, 1);
+      ret[key] = $.length > 0 ? fn($[0], key, ret) : undefined;
+    }
+  }
+
+  return ret as ExtractedMap<M>;
+}