6👍
Found the answer,
The Ajax results has to be parsed first.
resulting fix
var barChartData = JSON.parse(d);
17👍
The problem is that when your code executes, the canvas has not been created yet.
You should wrap your code inside a function and assign that function to window.onload event. You can see the sample code below.
window.onload = function() {
var ctx = document.getElementById("myChart");
var lineChart = new Chart(ctx, {
type: 'line',
data: {
labels: ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"],
datasets: [{
label: "2015",
data: [10, 8, 6, 5, 12, 8, 16, 17, 6, 7, 6, 10]
}]
}
})
}<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.5.0/Chart.js"></script>
</head>
<body>
<canvas id="myChart"></canvas>
</body>
</html>4👍
For other users who have this problem, make sure your container canvas element exists, when called upon.
4👍
running the following worked for me:
window.onload = function () {
}
2👍
You may try putting the Chart.JS script tag and other custom JS scripts just before the end of **<**/body> tag.
0👍
It looks like you’re using an object that doesn’t exist, well at least I cant see it, datasets. I can only see length being called on this object, unless there’s missing code?
I can see you assign d to barChartData
var barChartData = d;
So, you might want to replace the instances of datasets with barChartData.
0👍
It’s an old question but, I had this issue as well and in my case my data was length = 0. I solved this just adding a validation before calling the the graph:
if (barChartData.length > 0)
{
objChart = Morris.Bar({....
}
0👍
I faced the same error right after downloading & using a free bootstrap 5 admin template using the Chart JS package.
Chart.min.js:7 Uncaught TypeError: Cannot read properties of null (reading 'length')
at Object.acquireContext (Chart.min.js:7:76631)
at ni.construct (Chart.min.js:7:92209)
at new ni (Chart.min.js:7:91964)
at chart-area-demo.js:7:19
In my console:
This is the initial code:
// Set new default font family and font color to mimic Bootstrap's default styling
Chart.defaults.global.defaultFontFamily = '-apple-system,system-ui,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif';
Chart.defaults.global.defaultFontColor = '#292b2c';
// Area Chart Example
var ctx = document.getElementById("myAreaChart");
var myLineChart = new Chart(ctx, {
type: 'line',
data: {
labels: ["Mar 1", "Mar 2", "Mar 3", "Mar 4", "Mar 5", "Mar 6", "Mar 7", "Mar 8", "Mar 9", "Mar 10", "Mar 11", "Mar 12", "Mar 13"],
datasets: [{
label: "Sessions",
lineTension: 0.3,
backgroundColor: "rgba(2,117,216,0.2)",
borderColor: "rgba(2,117,216,1)",
pointRadius: 5,
pointBackgroundColor: "rgba(2,117,216,1)",
pointBorderColor: "rgba(255,255,255,0.8)",
pointHoverRadius: 5,
pointHoverBackgroundColor: "rgba(2,117,216,1)",
pointHitRadius: 50,
pointBorderWidth: 2,
data: [10000, 30162, 26263, 18394, 18287, 28682, 31274, 33259, 25849, 24159, 32651, 31984, 38451],
}],
},
options: {
scales: {
xAxes: [{
time: {
unit: 'date'
},
gridLines: {
display: false
},
ticks: {
maxTicksLimit: 7
}
}],
yAxes: [{
ticks: {
min: 0,
max: 40000,
maxTicksLimit: 5
},
gridLines: {
color: "rgba(0, 0, 0, .125)",
}
}],
},
legend: {
display: false
}
}
});
So what I did was to add a simple existence validation by using a conditional (IF). Like this:
// Set new default font family and font color to mimic Bootstrap's default styling
Chart.defaults.global.defaultFontFamily = '-apple-system,system-ui,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif';
Chart.defaults.global.defaultFontColor = '#292b2c';
// Area Chart Example
var ctx = document.getElementById("myAreaChart");
if (ctx) {
var myLineChart = new Chart(ctx, {
type: 'line',
data: {
labels: ["Mar 1", "Mar 2", "Mar 3", "Mar 4", "Mar 5", "Mar 6", "Mar 7", "Mar 8", "Mar 9", "Mar 10", "Mar 11", "Mar 12", "Mar 13"],
datasets: [{
label: "Sessions",
lineTension: 0.3,
backgroundColor: "rgba(2,117,216,0.2)",
borderColor: "rgba(2,117,216,1)",
pointRadius: 5,
pointBackgroundColor: "rgba(2,117,216,1)",
pointBorderColor: "rgba(255,255,255,0.8)",
pointHoverRadius: 5,
pointHoverBackgroundColor: "rgba(2,117,216,1)",
pointHitRadius: 50,
pointBorderWidth: 2,
data: [10000, 30162, 26263, 18394, 18287, 28682, 31274, 33259, 25849, 24159, 32651, 31984, 38451],
}],
},
options: {
scales: {
xAxes: [{
time: {
unit: 'date'
},
gridLines: {
display: false
},
ticks: {
maxTicksLimit: 7
}
}],
yAxes: [{
ticks: {
min: 0,
max: 40000,
maxTicksLimit: 5
},
gridLines: {
color: "rgba(0, 0, 0, .125)",
}
}],
},
legend: {
display: false
}
}
});
}
No more errors after that.