For an existing Angular 7 application, install the legacy Chart.js 2.9.4 package and create the chart in ngAfterViewInit against a canvas obtained with @ViewChild. Pinning the package matters: the current Chart.js release is 4.5.1, whose imports, registration, scales, and plugin options are different from the 2.x API used here. See the Chart.js version list and the 2.9.4 documentation.
Choose the legacy Angular 7 path
This tutorial targets an NgModule-based Angular 7 project, the TypeScript version already used by that project, and Chart.js 2.9.4. Angular 7 is a legacy framework release; use this combination to maintain an existing application rather than to start a new one.
Chart.js draws onto an HTML5 <canvas>. Angular supplies the component, template, lifecycle, and HTTP services. An optional wrapper such as ng2-charts adds Angular bindings, but direct Chart.js is the smallest and clearest solution for one or two charts.
Prerequisites
- An existing Angular 7 application and a Node.js/npm toolchain compatible with it.
- Basic Angular components, TypeScript, and templates.
- A browser with canvas support.
- An API endpoint only if your data is remote. Visual Studio, SQL Server, Entity Framework, and an ASP.NET Web API are not required for a local chart; they are backend choices in some older tutorials (source tutorial).
Install and verify Chart.js 2.9.4
In the Angular 7 project directory run:
npm install [email protected]
npm list chart.js
ng versionnpm install chart.js now selects the current package. Do not use that unpinned command with the 2.x code below. If you are creating a historical sample from scratch, use a matching Angular CLI rather than running a modern CLI and assuming it produced Angular 7:
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ng new chartjsdemo
cd chartjsdemo
npm install [email protected]
ng serveBuild one reusable chart component
Generate the component
ng generate component chartTemplate and sizing
Give each component its own canvas reference. Do not repeat a global id="canvas" when several charts can be rendered on one page.
<div class="chart-container">
<canvas #chartCanvas></canvas>
</div>.chart-container {
position: relative;
width: 100%;
height: 320px;
}A responsive canvas still needs a parent with a real height. Without one, percentage-based sizing can collapse or produce unexpected dimensions.
Component class with a bar chart
import {
AfterViewInit,
Component,
ElementRef,
OnDestroy,
ViewChild
} from '@angular/core';
import { Chart } from 'chart.js';
@Component({
selector: 'app-chart',
templateUrl: './chart.component.html',
styleUrls: ['./chart.component.css']
})
export class ChartComponent implements AfterViewInit, OnDestroy {
@ViewChild('chartCanvas') chartCanvas: ElementRef;
private chart: Chart;
ngAfterViewInit(): void {
const context = this.chartCanvas.nativeElement.getContext('2d');
this.chart = new Chart(context, {
type: 'bar',
data: {
labels: ['Red', 'Blue', 'Yellow', 'Green'],
datasets: [{
label: 'Votes',
data: [12, 19, 3, 5],
backgroundColor: ['#f44336', '#2196f3', '#ffeb3b', '#4caf50'],
borderWidth: 1
}]
},
options: {
responsive: true,
maintainAspectRatio: false,
legend: {
display: true,
position: 'bottom'
},
tooltips: {
enabled: true
},
scales: {
xAxes: [{
display: true
}],
yAxes: [{
ticks: {
beginAtZero: true
}
}]
}
}
});
}
ngOnDestroy(): void {
if (this.chart) {
this.chart.destroy();
}
}
}AfterViewInit runs after Angular has created the canvas; OnInit can run too early. Destroying the instance removes event handlers and releases chart resources when a route or component is replaced.
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Use typed data instead of strings
Keep labels and values separate, and keep numerical values numeric. String values can produce type inconsistencies and incorrect scale behavior.
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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesexport interface ChartPoint {
label: string;
value: number;
}
points: ChartPoint[] = [
{ label: 'January', value: 42 },
{ label: 'February', value: 58 },
{ label: 'March', value: 71 }
];
const labels = this.points.map(point => point.label);
const values = this.points.map(point => point.value);Change the chart type
For the same labels and dataset, change the type and add options appropriate to the visual question:
| Type | Best use | Typical data shape |
|---|---|---|
bar |
Compare categories | One value per label |
line |
Show a trend over ordered periods | Values aligned to dates or sequence labels |
pie |
Parts of one whole | One dataset whose values sum to a meaningful total |
doughnut |
Parts of a whole with a central hole | Same as pie |
polarArea |
Radial comparison of categories | One value per category |
radar |
Compare several dimensions | Values on shared named axes |
bubble |
Three numeric dimensions | {x, y, r} points |
scatter |
Relationship between two numeric variables | {x, y} points |
Line chart
type: 'line',
datasets: [{
label: 'Runs',
data: values,
borderColor: '#3cb371',
backgroundColor: 'rgba(60, 179, 113, 0.2)',
fill: true
}]For pie, doughnut, and polar-area charts, use the corresponding type and usually one dataset with a color per value. Keep category labels short and ensure the values represent a meaningful whole before choosing pie or doughnut.
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Load chart data from an API
Enable HttpClient
import { HttpClientModule } from '@angular/common/http';
@NgModule({
imports: [
BrowserModule,
HttpClientModule
]
})
export class AppModule {}Create a typed service
import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';
export interface PlayerStat {
PlayerName: string;
Run: number;
}
@Injectable()
export class ChartDataService {
constructor(private http: HttpClient) {}
getPlayerStats(): Observable<PlayerStat[]> {
return this.http.get<PlayerStat[]>('/api/charts');
}
}Use a same-origin URL where possible, or configure an Angular development proxy. Validate the response before rendering: require an array, reject null records, convert numeric strings deliberately, and handle an empty result separately from an error.
Render after the response and replace safely
private renderChart(labels: string[], values: number[]): void {
if (this.chart) {
this.chart.destroy();
}
const context = this.chartCanvas.nativeElement.getContext('2d');
this.chart = new Chart(context, {
type: 'line',
data: {
labels,
datasets: [{
label: 'Runs',
data: values,
borderColor: '#3cb371',
backgroundColor: 'rgba(60, 179, 113, 0.2)',
fill: true
}]
},
options: {
responsive: true,
maintainAspectRatio: false
}
});
}Call this method from the subscription after mapping the API response. Track loading, empty, and error states in the template, and do not append to label or value arrays on every emission without clearing or replacing them.
Direct Chart.js or ng2-charts?
Direct Chart.js has fewer dependencies, exposes the complete configuration object, and is straightforward for a small number of charts. Its trade-off is manual canvas access, updates, and cleanup.
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ng2-charts supplies Angular directives and bindings, which can reduce repetitive lifecycle code in a larger application. Wrapper APIs and peer dependencies change independently of Chart.js. The published compatibility information for ng2-charts 5.0.4 places Angular 2–9 on its v1.x line; do not install the current wrapper blindly in Angular 7. The project’s compatibility table is maintained in its repository.
Troubleshoot the common failures
Module not found
Run npm install [email protected], check npm list chart.js, and restart ng serve.
“Chart is not a constructor” or import errors
Check for a major-version mismatch or code copied from Chart.js 3/4. Either pin 2.9.4 for this API or rewrite for the modern API; do not mix them.
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“getContext of null”
Create the chart in ngAfterViewInit, use the component’s @ViewChild reference, and confirm the template has rendered. Duplicate IDs and incorrect selectors are common causes.
Blank chart
- Confirm the container has a visible height.
- Ensure labels and data arrays align.
- Ensure dataset values are numbers and the type is spelled correctly.
- Inspect the browser console and the actual API response.
Duplicate charts or repeated rendering
Destroy the previous instance before creating another and avoid pushing the same response into arrays on every observable emission.
CORS errors
The old tutorial demonstrates wildcard CORS with * (example). That can be acceptable for a local demonstration, but production APIs should restrict origins, methods, and headers. Prefer same-origin hosting or a development proxy.
Server-side rendering
Chart.js requires a browser canvas. Defer construction until browser execution and guard access to window, document, and the canvas when using Angular Universal or another pre-rendering setup.
Accessibility and production checks
- Give the chart a visible title and a text summary of the important result.
- Offer an accessible data table or downloadable data; canvas pixels are not a complete text alternative.
- Use sufficient contrast and do not communicate categories by color alone.
- Keep API validation and transport concerns in services rather than embedding database details in the chart component.
If you are starting a project today
Upgrade Angular instead of beginning a new Angular 7 application. Current Chart.js documentation uses registration for controllers, elements, scales, and plugins, or the convenience import chart.js/auto (integration guide). Its installation command is npm install chart.js (installation guide), but those current examples and option paths are not interchangeable with the Chart.js 2.9.4 code in this article.
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