Add `@astrojs/webapi` package (#2729)@astrojs/webapi@0.11.0

* chore: add @astrojs/webapi

* chore: update package.json

* fix: update file case

* fix: remove lowercase file

* chore: update tests to use mocha

* chore: update LICENSE

1 files changed, 32 insertions, 0 deletions

diff --git a/packages/webapi/src/lib/RelativeIndexingMethod.ts b/packages/webapi/src/lib/RelativeIndexingMethod.ts
new file mode 100644
index 000000000..56627dfc3
--- /dev/null
+++ b/packages/webapi/src/lib/RelativeIndexingMethod.ts
@@ -0,0 +1,32 @@
+type TypedArray = Int8Array | Uint8Array | Uint8ClampedArray | Int16Array | Uint16Array | Int32Array | Uint32Array | Float32Array | Float64Array | BigInt64Array | BigUint64Array
+
+export const at = {
+	at<T extends Array<any> | string | TypedArray>(this: T, index: number) {
+		index = Math.trunc(index) || 0
+	
+		if (index < 0) index += this.length;
+	
+		if (index < 0 || index >= this.length) return undefined;
+	
+		return this[index];
+	}
+}.at
+
+export const initRelativeIndexingMethod = (target: any, exclude: Set<string>) => {
+	if (exclude.has('at')) return
+
+	const Classes = []
+
+	if (!exclude.has('TypedArray')) Classes.push(Object.getPrototypeOf(target.Int8Array || globalThis.Int8Array))
+	if (!exclude.has('Array')) Classes.push(target.Array || globalThis.Array)
+	if (!exclude.has('String')) Classes.push(target.String || globalThis.String)
+
+	for (const Class of Classes) {
+		if (!Class.prototype.at) Object.defineProperty(Class.prototype, 'at', {
+			value: at,
+			writable: true,
+			enumerable: false,
+			configurable: true
+		})
+	}
+}