Code to show Arabic value in pdf doesn't work. It shows me some weird language that I don't understand:

var sm = {
    nature:[
        {name:"nature1",ar:"الطبيعة  1"},
        {name:"nature2",ar:"الطبيعة 2"},
        {name:"nature3",ar:"الطبيعة 3"},
        {name:"nature4",ar:"الطبيعة 4"}
    ],
    exportateur:[
        {name:"exportateur1",ar:"المصدر 1"},
        {name:"exportateur2",ar:"المصدر 2"},
        {name:"exportateur3",ar:"المصدر 3"},
        {name:"exportateur4",ar:"المصدر 4"}
    ],
    pays:[
        {name:"germany",ar:"ألمانيا"},
        {name:"france",ar:"فرنسا"},
        {name:"belgium",ar:"بلجيكا"},
        {name:"spain",ar:"إسبانيا"}
    ]
}
function createPdf(event){
    "use strict";
    var doc = new jsPDF();
    doc.text("Nature de la marchandise: "+sm.nature[0].ar,10, 10);
    doc.save("output.pdf");  
}

Result :