How to iterate over a list of items from Python/Flask using Javascript?
Question
I'm working to create a graph using HTML/JS/Python/Flask and the labels for this line graph should come from a list in Python and then I would use it on a Javascript.
So far I have not been able to successfully iterate over that list in Javascript, I'm getting 4 times the same string on my HTML.
I'm using a code similar to this one:
start.py
from flask import Flask, render_template
app = Flask(__name__)
@app.route('/', methods = ['GET','POST'])
def home():
data = ['ABC','DEF','GHI','JKL']
return render_template('index.html', data = data, len = len(data))
if __name__ == '__main__':
app.run(debug=True)
index.html
<body>
<p id='test'></p>
<script>
let text = '';
for (i=0; i<'{{len}}'; i++){
text += '{{data | tojson}}[i]' + '<br>'
}
console.log(text)
document.getElementById('test').innerHTML = text;
</script>
</body>
I'm getting this as an output:
['ABC','DEF','GHI','JKL'][i]
['ABC','DEF','GHI','JKL'][i]
['ABC','DEF','GHI','JKL'][i]
['ABC','DEF','GHI','JKL'][i]
And I'm looking to get this instead:
ABC
DEF
GHI
JKL
The data sent to the Javascript is sent as text and not as a list, if I change this:
text += '{{data | tojson}}[i]' + '<br>'
To this:
text += '{{data | tojson}}'[i] + '<br>'
The output becomes:
[
"
A
B
And the console output is:
[<br>"<br>A<br>B<br>
Do anybody know how to handle this properly so I get the correct results?
2 answers
solution1
0 2022-01-11 16:46:42
Try this in HTML
<body>
<p id='test'></p>
<script>
let text = '';
for (i=0; i<'{{len}}'; i++){
text += '{{data[i]}}' + '<br>'
}
console.log(text)
document.getElementById('test').innerHTML = text;
</script>
</body>
or you can also pass a string instead of an array.
from flask import Flask, render_template
app = Flask(__name__)
@app.route('/', methods = ['GET','POST'])
def home():
data = ['ABC','DEF','GHI','JKL']
return render_template('index.html', data = "\n".join(data), len = len(data))
if __name__ == '__main__':
app.run(debug=True)
and then in HTML you can just print this joined string
<body>
<p id='test'></p>
<script>
document.getElementById('test').innerHTML = {{data}};
</script>
</body>
solution2
0 2022-01-12 08:11:19
As you might have noticed, I'm a complete beginner when it comes to Javascript, doing some research, I found out I can slice and split in Javascript as well. So I solved my issue by using those two methods.
Giving more detail about what I did, {{data}} is passed over to Javascript as a single string, as '['ABC','DEF','GHI','JKL']', and if you read this string as a console output it shows:
['ABC', 'DEF', 'GHI', 'JKL']
To solve this I first sliced the string with:
flask_data = '{{data}}';
temp_array = flask_data.slice(6,-6);
So I get this as a result:
ABC', 'DEF', 'GHI', 'JKL
Then I split the string using the following substring: '', '', as follows:
array = temp_array.split('', '');
And as a result I got the array I needed:
['ABC','DEF','GHI','JKL']
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