better string coercion (#555)

Author: mbostock

src/curve.js

@@ -46,7 +46,7 @@ const curves = new Map([
 
 export function Curve(curve = curveLinear, tension) {
   if (typeof curve === "function") return curve; // custom curve
-  const c = curves.get((curve + "").toLowerCase());
+  const c = curves.get(`${curve}`.toLowerCase());
   if (!c) throw new Error(`unknown curve: ${curve}`);
   if (tension !== undefined) {
     switch (c) {

src/defined.js

@@ -13,7 +13,7 @@ export function descendingDefined(a, b) {
 }
 
 export function nonempty(x) {
-  return x != null && (x + "") !== "";
+  return x != null && `${x}` !== "";
 }
 
 export function filter(index, ...channels) {

src/mark.js

@@ -28,7 +28,7 @@ export class Mark {
         throw new Error(`missing channel value: ${name}`);
       }
       if (name !== undefined) {
-        const key = name + "";
+        const key = `${name}`;
         if (key === "__proto__") throw new Error("illegal channel name");
         if (names.has(key)) throw new Error(`duplicate channel: ${key}`);
         names.add(key);
@@ -49,7 +49,7 @@ export class Mark {
     }
     const channels = this.channels.map(channel => {
       const {name} = channel;
-      return [name == null ? undefined : name + "", Channel(data, channel)];
+      return [name == null ? undefined : `${name}`, Channel(data, channel)];
     });
     if (this.sort != null) channelSort(channels, facetChannels, data, this.sort);
     return {index, channels};
@@ -120,7 +120,7 @@ export const field = name => d => d[name];
 export const indexOf = (d, i) => i;
 export const identity = {transform: d => d};
 export const zero = () => 0;
-export const string = x => x == null ? x : x + "";
+export const string = x => x == null ? x : `${x}`;
 export const number = x => x == null ? x : +x;
 export const boolean = x => x == null ? x : !!x;
 export const first = d => d[0];
@@ -158,7 +158,7 @@ export function maybeKeyword(input, name, allowed) {
 
 // Validates the specified required string against the allowed list of keywords.
 export function keyword(input, name, allowed) {
-  const i = (input + "").toLowerCase();
+  const i = `${input}`.toLowerCase();
   if (!allowed.includes(i)) throw new Error(`invalid ${name}: ${input}`);
   return i;
 }

src/marks/link.js

@@ -44,7 +44,7 @@ export class Link extends Mark {
               c.point(X1[i], Y1[i]);
               c.point(X2[i], Y2[i]);
               c.lineEnd();
-              return p + "";
+              return `${p}`;
             })
             .call(applyChannelStyles, channels))
       .node();

src/scales/quantitative.js

@@ -39,7 +39,7 @@ const interpolators = new Map([
 ]);
 
 export function Interpolator(interpolate) {
-  const i = (interpolate + "").toLowerCase();
+  const i = `${interpolate}`.toLowerCase();
   if (!interpolators.has(i)) throw new Error(`unknown interpolator: ${i}`);
   return interpolators.get(i);
 }

src/scales/schemes.js

@@ -171,7 +171,7 @@ function schemei(interpolate) {
 }
 
 export function ordinalScheme(scheme) {
-  const s = (scheme + "").toLowerCase();
+  const s = `${scheme}`.toLowerCase();
   if (!ordinalSchemes.has(s)) throw new Error(`unknown scheme: ${s}`);
   return ordinalSchemes.get(s);
 }
@@ -235,7 +235,7 @@ const quantitativeSchemes = new Map([
 ]);
 
 export function quantitativeScheme(scheme) {
-  const s = (scheme + "").toLowerCase();
+  const s = `${scheme}`.toLowerCase();
   if (!quantitativeSchemes.has(s)) throw new Error(`unknown scheme: ${s}`);
   return quantitativeSchemes.get(s);
 }

src/transforms/group.js

@@ -178,7 +178,7 @@ export function maybeGroup(I, X) {
 export function maybeReduce(reduce, value) {
   if (reduce && typeof reduce.reduce === "function") return reduce;
   if (typeof reduce === "function") return reduceFunction(reduce);
-  switch ((reduce + "").toLowerCase()) {
+  switch (`${reduce}`.toLowerCase()) {
     case "first": return reduceFirst;
     case "last": return reduceLast;
     case "count": return reduceCount;

src/transforms/map.js

@@ -41,7 +41,7 @@ export function map(outputs = {}, options = {}) {
 function maybeMap(map) {
   if (map && typeof map.map === "function") return map;
   if (typeof map === "function") return mapFunction(map);
-  switch ((map + "").toLowerCase()) {
+  switch (`${map}`.toLowerCase()) {
     case "cumsum": return mapCumsum;
   }
   throw new Error("invalid map");

src/transforms/normalize.js

@@ -16,7 +16,7 @@ export function normalizeY(basis, options) {
 export function normalize(basis) {
   if (basis === undefined) return normalizeFirst;
   if (typeof basis === "function") return normalizeBasis((I, S) => basis(take(S, I)));
-  switch ((basis + "").toLowerCase()) {
+  switch (`${basis}`.toLowerCase()) {
     case "first": return normalizeFirst;
     case "last": return normalizeLast;
     case "mean": return normalizeMean;

src/transforms/stack.js

@@ -124,7 +124,7 @@ function stack(x, y = () => 1, ky, {offset, order, reverse}, options) {
 
 function maybeOffset(offset) {
   if (offset == null) return;
-  switch ((offset + "").toLowerCase()) {
+  switch (`${offset}`.toLowerCase()) {
     case "expand": case "normalize": return offsetExpand;
     case "center": case "silhouette": return offsetCenter;
     case "wiggle": return offsetWiggle;