flow like the river

VISUALIZACION/node_modules/d3-selection/src/selection/classed.js

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+function classArray(string) {
+  return string.trim().split(/^|\s+/);
+}
+
+function classList(node) {
+  return node.classList || new ClassList(node);
+}
+
+function ClassList(node) {
+  this._node = node;
+  this._names = classArray(node.getAttribute("class") || "");
+}
+
+ClassList.prototype = {
+  add: function(name) {
+    var i = this._names.indexOf(name);
+    if (i < 0) {
+      this._names.push(name);
+      this._node.setAttribute("class", this._names.join(" "));
+    }
+  },
+  remove: function(name) {
+    var i = this._names.indexOf(name);
+    if (i >= 0) {
+      this._names.splice(i, 1);
+      this._node.setAttribute("class", this._names.join(" "));
+    }
+  },
+  contains: function(name) {
+    return this._names.indexOf(name) >= 0;
+  }
+};
+
+function classedAdd(node, names) {
+  var list = classList(node), i = -1, n = names.length;
+  while (++i < n) list.add(names[i]);
+}
+
+function classedRemove(node, names) {
+  var list = classList(node), i = -1, n = names.length;
+  while (++i < n) list.remove(names[i]);
+}
+
+function classedTrue(names) {
+  return function() {
+    classedAdd(this, names);
+  };
+}
+
+function classedFalse(names) {
+  return function() {
+    classedRemove(this, names);
+  };
+}
+
+function classedFunction(names, value) {
+  return function() {
+    (value.apply(this, arguments) ? classedAdd : classedRemove)(this, names);
+  };
+}
+
+export default function(name, value) {
+  var names = classArray(name + "");
+
+  if (arguments.length < 2) {
+    var list = classList(this.node()), i = -1, n = names.length;
+    while (++i < n) if (!list.contains(names[i])) return false;
+    return true;
+  }
+
+  return this.each((typeof value === "function"
+      ? classedFunction : value
+      ? classedTrue
+      : classedFalse)(names, value));
+}