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backend/node_modules/mnemonist/utils/iterables.js

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+/**
+ * Mnemonist Iterable Function
+ * ============================
+ *
+ * Harmonized iteration helpers over mixed iterable targets.
+ */
+var forEach = require('obliterator/foreach');
+
+var typed = require('./typed-arrays.js');
+
+/**
+ * Function used to determine whether the given object supports array-like
+ * random access.
+ *
+ * @param  {any} target - Target object.
+ * @return {boolean}
+ */
+function isArrayLike(target) {
+  return Array.isArray(target) || typed.isTypedArray(target);
+}
+
+/**
+ * Function used to guess the length of the structure over which we are going
+ * to iterate.
+ *
+ * @param  {any} target - Target object.
+ * @return {number|undefined}
+ */
+function guessLength(target) {
+  if (typeof target.length === 'number')
+    return target.length;
+
+  if (typeof target.size === 'number')
+    return target.size;
+
+  return;
+}
+
+/**
+ * Function used to convert an iterable to an array.
+ *
+ * @param  {any}   target - Iteration target.
+ * @return {array}
+ */
+function toArray(target) {
+  var l = guessLength(target);
+
+  var array = typeof l === 'number' ? new Array(l) : [];
+
+  var i = 0;
+
+  // TODO: we could optimize when given target is array like
+  forEach(target, function(value) {
+    array[i++] = value;
+  });
+
+  return array;
+}
+
+/**
+ * Same as above but returns a supplementary indices array.
+ *
+ * @param  {any}   target - Iteration target.
+ * @return {array}
+ */
+function toArrayWithIndices(target) {
+  var l = guessLength(target);
+
+  var IndexArray = typeof l === 'number' ?
+    typed.getPointerArray(l) :
+    Array;
+
+  var array = typeof l === 'number' ? new Array(l) : [];
+  var indices = typeof l === 'number' ? new IndexArray(l) : [];
+
+  var i = 0;
+
+  // TODO: we could optimize when given target is array like
+  forEach(target, function(value) {
+    array[i] = value;
+    indices[i] = i++;
+  });
+
+  return [array, indices];
+}
+
+/**
+ * Exporting.
+ */
+exports.isArrayLike = isArrayLike;
+exports.guessLength = guessLength;
+exports.toArray = toArray;
+exports.toArrayWithIndices = toArrayWithIndices;