fix typings issues (ARROW-1903)

Author: trxcllnt

js/src/text-encoding-utf-8.d.ts

@@ -34,10 +34,10 @@ export class NumericVector<T, TArray extends TypedArray> extends Vector<T> {
     concat(...vectors: Vector<T>[]): Vector<T> {
         return new VirtualVector(this.data.constructor as TypedArrayConstructor, this, ...vectors);
     }
-    slice(start?: number, end?: number) {
+    slice<R = TArray>(start?: number, end?: number): R {
         const { data, stride } = this, from = start! | 0;
         const to = end === undefined ? data.length : Math.max(end | 0, from);
-        return data.subarray(Math.min(from, to) * stride | 0, to * stride | 0);
+        return data.subarray(Math.min(from, to) * stride | 0, to * stride | 0) as any as R;
     }
 }
 
@@ -49,7 +49,8 @@ export class FixedWidthNumericVector<T, TArray extends TypedArray> extends Numer
 
 export class BoolVector extends NumericVector<boolean, Uint8Array> {
     static pack(values: Iterable<any>) {
-        let xs = [], n, i = 0;
+        let n = 0, i = 0;
+        let xs: number[] = [];
         let bit = 0, byte = 0;
         for (const value of values) {
             value && (byte |= 1 << bit);

js/src/vector/numeric.ts

@@ -93,7 +93,7 @@ export class VirtualVector<T> implements Vector<T> {
                 // this is a significant improvement as we avoid the memcpy 🎉
                 if ((source.length / vector.stride | 0) < total) {
                     let vectorsLength = vectors.length;
-                    let count = 0, length = 0, sources = [];
+                    let count = 0, length = 0, sources = [] as any[];
                     do {
                         sources.push(source);
                         length += source.length;

js/src/vector/virtual.ts

@@ -16,7 +16,7 @@
 // under the License.
 
 /* tslint:disable */
-// Dynamically load an Ix target build based on command line arguments
+// Dynamically load an Arrow target build based on command line arguments
 
 const path = require('path');
 const target = process.env.TEST_TARGET!;

js/test/Arrow.ts

@@ -37,7 +37,7 @@ const arrowBuffers: Uint8Array[] = [fs.readFileSync(arrowPath)];
 
 import Arrow from '../Arrow';
 import { zip } from 'ix/iterable/zip';
-import { toArray } from 'ix/iterable/toArray';
+import { toArray } from 'ix/iterable/toarray';
 
 const { Table, read } = Arrow;