flow like the river

BACK_BACK/node_modules/d3-scale/src/identity.js

@@ -0,0 +1,28 @@
+import {linearish} from "./linear.js";
+import number from "./number.js";
+
+export default function identity(domain) {
+  var unknown;
+
+  function scale(x) {
+    return x == null || isNaN(x = +x) ? unknown : x;
+  }
+
+  scale.invert = scale;
+
+  scale.domain = scale.range = function(_) {
+    return arguments.length ? (domain = Array.from(_, number), scale) : domain.slice();
+  };
+
+  scale.unknown = function(_) {
+    return arguments.length ? (unknown = _, scale) : unknown;
+  };
+
+  scale.copy = function() {
+    return identity(domain).unknown(unknown);
+  };
+
+  domain = arguments.length ? Array.from(domain, number) : [0, 1];
+
+  return linearish(scale);
+}