How to Set Dynamic Properties to Variable in TypeScript? [duplicate]

I'm trying to set some dynamic properties to a variable in typescript. The problem I'm facing is when I try to set it I run into the error "uncaught TypeError: Cannot set properties of undefined (setting 'varname')" It needs to be set on this variable as it is used to render some other data on the page, I also cannot define a model for the data as I do not know how many properties will be returned or there name/values. How can I assign dynamic properties to my variable. Ex code

// will be dynamic properties in use case
var tValue = 500
var tName = "donuts"
var tArray = [2, 4, 9, 55];

window.onload = (event) => {
let x;
// trying to set variables will throw error cannot set properties of undefned
x.tree = tValue;
x.header = tName;
x.time = tArray;
}


Example JS Fiddle: https://jsfiddle.net/mtj6L3zq/

Continue reading...