Hmm, interesting. I literally copied and pasted your code and ran it to get this error. Just in case I accidentally fat fingered something, I’m pasting the code below. As for your tip about debugging client side callbacks, thank you for that. First, let me say that I am fairly novice. I think one of the benefits of python is it’s low barrier to entry, but that is also one of the challenges. I just felt like I was hitting my stride, then I jumped into Dash with callbacks and decorators, it kind of feels like I accidentally took an upper division class as a freshman. 
So, given that I already have your function below in the clientside_callback would I add this debugging language in your function to your existing function? Or, am I misunderstanding the idea of the app callback, in other words, can I have more than one callback?
Also, your point about right click> inspect element, thanks I was using Safari before which lacks that functionality. I flipped over to Chrome. If it matters, the error is persistent.
import dash
from dash.dependencies import Output, Input, State
import dash_core_components as dcc
import dash_html_components as html
import plotly.graph_objs as go
import numpy as np
import pandas as pd
import datetime
#some random values
a = datetime.datetime.today()
numdays = 100
dateList = []
for x in range (0, numdays):
dateList.append(a - datetime.timedelta(days = x))
xy = [dateList,np.random.rand(100)]
df = pd.DataFrame(data=xy[1],columns=["y"],index=xy[0])
#Graph data
dataS = [dict(
x = df.index,
y = df['y'],
name = 'meter',
mode = 'lines'
)]
#Graph layout
layoutS = go.Layout(
title="Meter",
xaxis=dict(
rangeslider_visible=True,
rangeselector=dict(
buttons=list([
dict(count=1, label="1m", step="month", stepmode="backward"),
dict(count=6, label="6m", step="month", stepmode="backward"),
dict(count=1, label="YTD", step="year", stepmode="todate"),
dict(count=1, label="1y", step="year", stepmode="backward"),
dict(count=5, label="5y", step="year", stepmode="backward"),
dict(step="all")
])
)
),
yaxis=dict(range=[0,2])
)
#Dash app layout
app = dash.Dash()
app.title = 'Random'
app.layout = html.Div(
html.Div([
html.H1(children='Random nums'),
html.Div(children='''
Rand rand rand.
'''),
dcc.Input(
id='input-y',
placeholder='Insert y value',
type='number',
value='',
),
html.Div(id='result'),
dcc.Graph(id='RandGraph',figure=dict(data=dataS,layout=layoutS))
])
)
#client side implementation
app.clientside_callback(
"""
function(relOut, Figure) {
if (typeof relOut !== 'undefined') {
if (typeof relOut["xaxis.range"] !== 'undefined') {
//get active filter from graph
fromS = new Date(relOut["xaxis.range"][0]).getTime()
toS = new Date(relOut["xaxis.range"][1]).getTime()
xD = Figure.data[0].x
yD = Figure.data[0].y
//filter y data with graph display
yFilt = xD.reduce(function (pV,cV,cI){
sec = new Date(cV).getTime()
if (sec >= fromS && sec <= toS) {
pV.push(yD[cI])
}
return pV
}, [])
yMax = Math.max.apply(Math, yFilt)
yMin = Math.min.apply(Math, yFilt)
} else {
yMin = Math.min.apply(Math, Figure.data[0].y)
yMax = Math.max.apply(Math, Figure.data[0].y)
}
} else {
yMin = Math.min.apply(Math, Figure.data[0].y)
yMax = Math.max.apply(Math, Figure.data[0].y)
}
Figure.layout.yaxis = {
'range': [yMin,yMax],
'type': 'linear'
}
return {'data': Figure.data, 'layout': Figure.layout};
}
""",
Output('RandGraph','figure'),
[Input('RandGraph','relayoutData')],[State('RandGraph', 'figure')]
)
#Server side implementation (slow)
#@app.callback(
# Output('RandGraph','figure'),
# [Input('RandGraph','relayoutData')],[State('RandGraph', 'figure')]
#)
#def update_result(relOut,Fig):
# ymin = df.loc[relOut['xaxis.range'][1]:relOut['xaxis.range'][0],'y'].min()
# ymax = df.loc[relOut['xaxis.range'][1]:relOut['xaxis.range'][0],'y'].max()
# newLayout = go.Layout(
# title="OL Meter",
# xaxis=dict(
# rangeslider_visible=True,
# rangeselector=dict(
# buttons=list([
# dict(count=0, label="1m", step="month", stepmode="backward"),
# dict(count=6, label="6m", step="month", stepmode="backward"),
# dict(count=1, label="YTD", step="year", stepmode="todate"),
# dict(count=1, label="1y", step="year", stepmode="backward"),
# dict(count=5, label="5y", step="year", stepmode="backward"),
# dict(step="all")
# ])
# ),
# range=relOut['xaxis.range']
# ),
# yaxis=dict(range=[ymin,ymax])
# )
#
#
# Fig['layout']=newLayout
# return Fig
if __name__ == '__main__':
app.run_server(debug=False)