I wanted to set up a fake API that gives me test data and find out how long does my javascript function (that is wrapped deep inside some react components) execute.
Python - fake API
server.py:
from flask import Flask, jsonify
from flask_cors import CORS
app = Flask(__name__)
cors = CORS(app)
@app.route('/get-data', methods=['GET'])
def get_data():
data = getData() # generate fake data, much bigger than real
return jsonify(data)
if __name__ == "__main__":
app.run()
Javascript - index.html
<html>
<body>
<script>
function doExpensiveThings() {
...
}
fetch('http://localhost:5000/get-data', {mode: 'cors'}).then(response => {
response.json().then(jsonResponse => {
console.time("doExpensiveThings");
doExpensiveThings(jsonResponse);
console.timeEnd("doExpensiveThings");
}).catch(err => {
console.warn(err);
})
}).catch(err => {
console.warn(err);
})
</script>
</body>
</html>
And then in the console, one would see: doExpensiveThings: 1.3291015625 ms.
fetch returns a promise, if everything went alright, the promise is resolved and the value is an instance of the Response class. I wanted to parse the response as json, so I called .json() method on the instance, this again returns a promise.
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