I'm using chart.js to make a tracker program. The chart here takes in user input values and produces a chart. I want it users to be able to save the values in localStorage, which I can successfully do. The problem lies in the retrieval of chart values and producing the chart. I've tried using the chart.update(); and chart.render(); functions but they do not create the chart. How do I fix this?
HTML
```<div style="float: left; margin-left: 80px; margin-top: 13px; text-align: center; padding-bottom: 530px; margin-bottom: 20px; padding-top: 10px;">
<form>
<!---Monday--->
<div >
<p style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">Monday</p>
<input type="integer" name="monday" id="monday" placeholder="Monday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!---Tuesday--->
<div >
<p style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">Tuesday</p>
<input type="integer" name="tuesday" id="tuesday" placeholder="Tuesday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!---Wednesday--->
<div >
<p style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">Wednesday</p>
<input type="integer" name="wednesday" id="wednesday" placeholder="Wednesday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!---Thursday--->
<div >
<p style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">Thursday</p>
<input type="integer" name="thursday" id="thursday" placeholder="Thursday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!---Friday--->
<div >
<p style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">Friday</p>
<input type="integer" name="friday" id="friday" placeholder="Friday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!---Saturday--->
<div >
<p style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">Saturday</p>
<input type="integer" name="saturday" id="saturday" placeholder="Saturday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!---Sunday--->
<div >
<p style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">Sunday</p>
<input type="integer" name="sunday" id="sunday" placeholder="Sunday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
</form>
<!---Save and clear buttons for local storage--->
<div>
<button id="save-btn">Save</button>
<button id="clear-btn">Clear</button>
</div>
</div>```
JAVASCRIPT
```<script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
<div style=" float: right; margin-right: 100px; position: relative; height: 60vh; width: 60vw; margin-top: 100px">
<canvas id="myChart" width="100px" height="100px"></canvas>
<script>
//Chart setup and configuration
let chartData =[]
const ctx = document.getElementById('myChart');
const myChart = new Chart(ctx, {
type: 'bar',
data: {
labels: ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'],
datasets: [{
label: 'Hours of sleep',
data: chartData,
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)',
'rgba(222, 184, 135, 0.2)'
],
borderColor: [
'rgba(255, 99, 132, 1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)',
'rgba(222, 184, 135, 1)'
],
borderWidth: 1
}]
},
options: {
scales: {
y: {
beginAtZero: true
}
}
}
});
//Removing general data
function removeData(chart) {
chart.data.datasets.forEach((dataset) => {
dataset.data.pop();
});
chart.update();
}
//Adding user data in
function addData(chart, data) {
chart.data.datasets.forEach((dataset) => {
dataset.data = [...data]
});
chart.update();
}
//Calling input values to update chart
function updateChart(event){
event.preventDefault()
monValue = Number(document.getElementById('monday').value);
tuesValue = Number(document.getElementById('tuesday').value);
wedValue = Number(document.getElementById('wednesday').value);
thursValue = Number(document.getElementById('thursday').value);
friValue = Number(document.getElementById('friday').value);
satValue = Number(document.getElementById('saturday').value);
sunValue = Number(document.getElementById('sunday').value);
chartData = [
monValue,
tuesValue,
wedValue,
thursValue,
friValue,
satValue,
sunValue
]
removeData(myChart)
addData(myChart, chartData)
}
//Updating chart with values
var sleepBtn = document.querySelectorAll('.sleep-btn');
sleepBtn.forEach(btn => {
btn.addEventListener('click', updateChart, false)
})
//Local storage functions
const saveButton = document.querySelector('.save-btn');
const clearButton = document.querySelector('.clear-btn');
const dataPoints = JSON.parse(window.localStorage.getItem("sdps"));
function storageValues(){
myChart.update(myChart, sdps);
chart.render();
}
const saveToLocalStorage = () =>{
window.localStorage.setItem('sdps', JSON.stringify(chartData));
}
function clearStorage(){
localStorage.clear();
};
saveButton.addEventListener('click', saveToLocalStorage);
clearButton.addEventListener('click', clearStorage);
</script>
</div>```
CodePudding user response：
I'd approach this by setting the initial state of the UI based on the localStorage values.
let chartData = loadFromLocalStorage();
setUIData(chartData);
Then I'd have all the enter buttons and the Save button do essentially the same thing: get the current data from the UI, save it to localStorage, and then update the chart.
function updateChart(event) {
if (event) event.preventDefault();
chartData = getUIData();
saveToLocalStorage(chartData);
addData(myChart, chartData);
}
The full code looks like the following. See working example at https://jsbin.com/bujomeliho/3/edit?html,output (I would have used the embedded snippets here on SO but localStorage is disallowed.)
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
<div
style="float: left; margin-left: 80px; margin-top: 13px; text-align: center; padding-bottom: 530px; margin-bottom: 20px; padding-top: 10px;">
<form>
<!-- Monday -->
<div >
<p
style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">
Monday</p>
<input type="number" name="monday" id="monday" placeholder="Monday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!-- Tuesday -->
<div >
<p
style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">
Tuesday</p>
<input type="number" name="tuesday" id="tuesday" placeholder="Tuesday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!-- Wednesday -->
<div >
<p
style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">
Wednesday</p>
<input type="number" name="wednesday" id="wednesday" placeholder="Wednesday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!-- Thursday -->
<div >
<p
style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">
Thursday</p>
<input type="number" name="thursday" id="thursday" placeholder="Thursday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!-- Friday -->
<div >
<p
style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">
Friday</p>
<input type="number" name="friday" id="friday" placeholder="Friday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!-- Saturday -->
<div >
<p
style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">
Saturday</p>
<input type="number" name="saturday" id="saturday" placeholder="Saturday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
<!-- Sunday -->
<div >
<p
style="color: #55725d; font-size: 20px; text-align: left; font-style: bold; margin-bottom: 4px; text-align: center; margin-top: 18px;">
Sunday</p>
<input type="number" name="sunday" id="sunday" placeholder="Sunday" value="">
<button style="margin-left: 78px;">Enter</button>
</div>
</form>
<!-- Save and clear buttons for local storage -->
<div>
<button id="save-btn">Save</button>
<button id="clear-btn">Clear</button>
</div>
</div>
<div
style=" float: right; margin-right: 100px; position: relative; height: 60vh; width: 60vw; margin-top: 100px">
<canvas id="myChart" width="100px" height="100px"></canvas>
</div>
<script>
//Chart setup and configuration
let chartData = loadFromLocalStorage();
setUIData(chartData);
const ctx = document.getElementById('myChart');
const myChart = new Chart(ctx, {
type: 'bar',
data: {
labels: ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'],
datasets: [{
label: 'Hours of sleep',
data: chartData,
backgroundColor: [
'rgba(255, 99, 132, 0.2)',
'rgba(54, 162, 235, 0.2)',
'rgba(255, 206, 86, 0.2)',
'rgba(75, 192, 192, 0.2)',
'rgba(153, 102, 255, 0.2)',
'rgba(255, 159, 64, 0.2)',
'rgba(222, 184, 135, 0.2)'
],
borderColor: [
'rgba(255, 99, 132, 1)',
'rgba(54, 162, 235, 1)',
'rgba(255, 206, 86, 1)',
'rgba(75, 192, 192, 1)',
'rgba(153, 102, 255, 1)',
'rgba(255, 159, 64, 1)',
'rgba(222, 184, 135, 1)'
],
borderWidth: 1
}]
},
options: {
scales: {
y: {
beginAtZero: true
}
}
}
});
//Adding user data in
function addData(chart, data) {
chart.data.datasets.forEach((dataset) => {
dataset.data = [...data]
});
chart.update();
}
//Calling input values to update chart
function updateChart(event) {
if (event) event.preventDefault();
chartData = getUIData();
saveToLocalStorage(chartData);
addData(myChart, chartData);
}
//Updating chart with values
document.querySelectorAll('.sleep-btn').forEach(btn => {
btn.addEventListener('click', updateChart);
});
function setUIData(data) {
document.querySelectorAll('.sleep input').forEach((el, i) => el.value = data[i] || '');
}
function getUIData() {
return Array.from(document.querySelectorAll('.sleep input'))
.map(el => Number(el.value));
}
//Local storage functions
function loadFromLocalStorage() {
return JSON.parse(localStorage.getItem('sdps') || '[]');
}
function saveToLocalStorage(chartData) {
localStorage.setItem('sdps', JSON.stringify(chartData));
}
function clearStorage() {
localStorage.clear();
setUIData(['','','','','','','']);
updateChart();
};
document.querySelector('.save-btn').addEventListener('click', updateChart);
document.querySelector('.clear-btn').addEventListener('click', clearStorage);
</script>
</body>
</html>