How can I check if a script file has been loaded using jquery? [duplicate]

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• Verify External Script Is Loaded 6 answers

Im using the following to show/hide <section> of my page, I use the following on cllick to load some charts when the "Charts" button is clicked:

$(document).ready(function(){
    $("#graph_btn").on("click", function(){
        $(".table").hide();
        $(".charts").show();
        $.getScript("/js/charts.js");
    });
});

The problem is that if i click to show the results table, then i click to load the charts again, they are reloaded again and overlap each other, how can i wrap than getScriptin an If statement to check if the button has already been loaded? is this possible and if so can i include it in this .click function pr do I need to have a separate function? thanks