JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" id="search" value="Buscar" />

JavaScript

String.prototype.toSlug = function(){
    str = this.replace(/^\s+|\s+$/g, ''); // trim
    str = str.toLowerCase();
      
    // remove accents, swap ñ for n, etc
    var from = "ãàáäâèéëêìíïîõòóöôùúüûñç·/_,:;";
    var to   = "aaaaaeeeeiiiiooooouuuunc------";
    for (var i=0, l=from.length ; i<l ; i++) {
        str = str.replace(new RegExp(from.charAt(i), 'g'), to.charAt(i));
    }
 
    str = str.replace(/[^a-z0-9 -]/g, '').replace(/\s+/g, '-').replace(/-+/g, '-');
 
    return str;
};


String.prototype.toSearch = function(query) {
    var str = this.toSlug();
    
    return this.toSlug().search(new RegExp(query.toLowerCase(), 'i'));
};


var str = 'São Paulo';

$('#search').click(function() {
    alert(str.toSearch('Paulo'));
});