Chartjs-How to pass a array from node to .js file (pugJs)

You need to use unescaped string interpolation and a stringify to turn your pug variable into a client-side browser variable:

var arrayForChart = !{JSON.stringify(arrayInPug)};

If the variable in express/pug is ['a', 'b', 'c'] then this will output:

var arrayForChart = ['a', 'b', 'c'];

Without the stringify you’ll get something like this which will just throw an error in the browser as it’s not valid JavaScript:

var arrayForChart = [Object object];