html - Swift - execute Javascript on each page -

i have uiwebview pass html file load.

the html file includes javascript looks existence of variable. if exists, performs 1 action, if variable doesn't exist, script performs action.

if(typeof customvar === 'undefined')   //perform task1 else   // perform task 2 using customvar 

on native, use function stringbyevaluatingjavascriptfromstring set variable before page loaded. so, i'm setting code in webviewdidstartload (i tried place in shouldstartloadwithrequest).

func webviewdidstartload(webview: uiwebview) {     let cutvar = "test"     webview.stringbyevaluatingjavascriptfromstring("customvar = '\(cutvar)';") } 

this works when load page first time, first time. after that, seems through webviewdidstartload, re-assign variable in current page, , reload page itself. means, page reloaded without variable set.

is there way want run javascript bit next page load? maybe global variable accessible?

thank you.