Remove createElement and pre-allocate arrays (#6788)

* Remove createElement and pre-allocate arrays

* Address review comment

diff --git a/docs/getting-started/v3-migration.md b/docs/getting-started/v3-migration.md
index 1ce1f146c67f6c1b487e6b2d2361471c1a079d85..ffa87614f9f374211ba58b65a1721a596cdb909b 100644 (file)
--- a/docs/getting-started/v3-migration.md
+++ b/docs/getting-started/v3-migration.md
@@ -70,6 +70,8 @@ Chart.js 3.0 introduces a number of breaking changes. Chart.js 2.0 was released
 * `Chart.chart.chart`
 * `Chart.types`
 * `DatasetController.addElementAndReset`
+* `DatasetController.createMetaData`
+* `DatasetController.createMetaDataset`
 * `Element.getArea`
 * `Element.height`
 * `Element.initialize`
@@ -104,7 +106,6 @@ Chart.js 3.0 introduces a number of breaking changes. Chart.js 2.0 was released
 * `helpers.log10` was renamed to `helpers.math.log10`
 * `Chart.Animation.animationObject` was renamed to `Chart.Animation`
 * `Chart.Animation.chartInstance` was renamed to `Chart.Animation.chart`
-* `DatasetController.createMetaData` and `DatasetController.createMetaDataset` were replaced with `DatasetController.createElement`
 * `DatasetController.updateElement` was renamed to `DatasetController.updateElements`
 * `TimeScale.getLabelCapacity` was renamed to `TimeScale._getLabelCapacity`
 * `TimeScale.tickFormatFunction` was renamed to `TimeScale._tickFormatFunction`

diff --git a/src/core/core.datasetController.js b/src/core/core.datasetController.js
index 43350bb6062bcfbe7ac2bc6b769ead36c9952c22..b4f7099196f23cc76cdcf371ea694b7400558b6e 100644 (file)
--- a/src/core/core.datasetController.js
+++ b/src/core/core.datasetController.js
@@ -153,15 +153,15 @@ function applyStack(stack, value, dsIndex, allOther) {
 }
 
 function convertObjectDataToArray(data) {
-       var keys = Object.keys(data);
-       var adata = [];
-       var i, ilen, key;
+       const keys = Object.keys(data);
+       const adata = new Array(keys.length);
+       let i, ilen, key;
        for (i = 0, ilen = keys.length; i < ilen; ++i) {
                key = keys[i];
-               adata.push({
+               adata[i] = {
                        x: key,
                        y: data[key]
-               });
+               };
        }
        return adata;
 }
@@ -358,17 +358,13 @@ helpers.extend(DatasetController.prototype, {
                }
        },
 
-       createElement: function(type) {
-               return type && new type();
-       },
-
        /**
         * @private
         */
        _dataCheck: function() {
-               var me = this;
-               var dataset = me.getDataset();
-               var data = dataset.data || (dataset.data = []);
+               const me = this;
+               const dataset = me.getDataset();
+               const data = dataset.data || (dataset.data = []);
 
                // In order to correctly handle data addition/deletion animation (an thus simulate
                // real-time charts), we need to monitor these data modifications and synchronize
@@ -420,19 +416,21 @@ helpers.extend(DatasetController.prototype, {
        },
 
        addElements: function() {
-               var me = this;
-               var meta = me._cachedMeta;
-               var metaData = meta.data;
-               var i, ilen, data;
+               const me = this;
+               const meta = me._cachedMeta;
+               let i, ilen, data;
 
                me._dataCheck();
                data = me._data;
+               const metaData = meta.data = new Array(data.length);
 
                for (i = 0, ilen = data.length; i < ilen; ++i) {
-                       metaData[i] = metaData[i] || me.createElement(me.dataElementType);
+                       metaData[i] = new me.dataElementType();
                }
 
-               meta.dataset = meta.dataset || me.createElement(me.datasetElementType);
+               if (me.datasetElementType) {
+                       meta.dataset = new me.datasetElementType();
+               }
        },
 
        buildOrUpdateElements: function() {
@@ -516,14 +514,15 @@ helpers.extend(DatasetController.prototype, {
                const vId = vScale.id;
                const labels = iScale._getLabels();
                const singleScale = iScale === vScale;
-               const parsed = [];
-               let i, ilen, item;
+               const parsed = new Array(count);
+               let i, ilen, index;
 
-               for (i = start, ilen = start + count; i < ilen; ++i) {
-                       item = {};
-                       item[iId] = singleScale || iScale._parse(labels[i], i);
-                       item[vId] = vScale._parse(data[i], i);
-                       parsed.push(item);
+               for (i = 0, ilen = count; i < ilen; ++i) {
+                       index = i + start;
+                       parsed[i] = {
+                               [iId]: singleScale || iScale._parse(labels[index], index),
+                               [vId]: vScale._parse(data[index], index)
+                       };
                }
                return parsed;
        },
@@ -543,14 +542,16 @@ helpers.extend(DatasetController.prototype, {
                const {xScale, yScale} = meta;
                const xId = xScale.id;
                const yId = yScale.id;
-               const parsed = [];
-               let i, ilen, item;
-               for (i = start, ilen = start + count; i < ilen; ++i) {
-                       item = data[i];
-                       parsed.push({
-                               [xId]: xScale._parse(item[0], i),
-                               [yId]: yScale._parse(item[1], i)
-                       });
+               const parsed = new Array(count);
+               let i, ilen, index, item;
+
+               for (i = 0, ilen = count; i < ilen; ++i) {
+                       index = i + start;
+                       item = data[index];
+                       parsed[i] = {
+                               [xId]: xScale._parse(item[0], index),
+                               [yId]: yScale._parse(item[1], index)
+                       };
                }
                return parsed;
        },
@@ -570,14 +571,16 @@ helpers.extend(DatasetController.prototype, {
                const {xScale, yScale} = meta;
                const xId = xScale.id;
                const yId = yScale.id;
-               const parsed = [];
-               let i, ilen, item;
-               for (i = start, ilen = start + count; i < ilen; ++i) {
-                       item = data[i];
-                       parsed.push({
-                               [xId]: xScale._parseObject(item, 'x', i),
-                               [yId]: yScale._parseObject(item, 'y', i)
-                       });
+               const parsed = new Array(count);
+               let i, ilen, index, item;
+
+               for (i = 0, ilen = count; i < ilen; ++i) {
+                       index = i + start;
+                       item = data[index];
+                       parsed[i] = {
+                               [xId]: xScale._parseObject(item, 'x', index),
+                               [yId]: yScale._parseObject(item, 'y', index)
+                       };
                }
                return parsed;
        },
@@ -958,14 +961,15 @@ helpers.extend(DatasetController.prototype, {
         */
        insertElements: function(start, count) {
                const me = this;
-               const elements = [];
+               const elements = new Array(count);
                const data = me._cachedMeta.data;
                let i;
 
-               for (i = start; i < start + count; ++i) {
-                       elements.push(me.createElement(me.dataElementType));
+               for (i = 0; i < count; ++i) {
+                       elements[i] = new me.dataElementType();
                }
                data.splice(start, 0, ...elements);
+
                me._parse(start, count);
                me.updateElements(data, start, count);
        },