Javascript - How do "IF and Else" work in conjunction with "returns"?

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Javascript - How do "IF and Else" work in conjunction with "returns"?

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#1 by (1 votes)

1

I'm having a hard time understanding why sometimes, depending on where an "if" statement is inserted into a particular block of a function, it is ignored. And how to use the "retuns", when it is desired within that expressions to stop, forward or return a certain function?

For example:

In this code, everything happens, as expected, however, the cursor is locked in the input and does not advance to another field with TAB or clicking, is locked in focus, now in the next example:

function nome_existe() {
	
	if(!valida_nome()) { // caso seja inválido
	document.getElementById("input_nome_cad").focus();
	return;
	}
	var nome = document.getElementById("input_nome_cad").value;
	var xmlreq = CriaRequest();
	xmlreq.open("GET", "mysqli_select_ajax.php?nome_cad=" + nome, true);
	xmlreq.onreadystatechange = function(){
		if (xmlreq.readyState == 4 && xmlreq.status == 200){
	    	document.getElementById("input_nome_cad").value='';
			document.getElementById("input_nome_cad").placeholder = xmlreq.responseText;
		}
		if(document.getElementById("input_nome_cad").placeholder == "Nome já existe!"){
			document.getElementById("input_nome_cad").placeholder = "Troca o nome";
		}
	}
	document.getElementById("input_nome_cad").focus();
	xmlreq.send(null);
	
}

In this example I added a new "if" that is ignored, how do these checks work?

function nome_existe() {
	
	if(!valida_nome()) { // caso seja inválido
	document.getElementById("input_nome_cad").focus();
	return;
	}
	var nome = document.getElementById("input_nome_cad").value;
	var xmlreq = CriaRequest();
	xmlreq.open("GET", "mysqli_select_ajax.php?nome_cad=" + nome, true);
	xmlreq.onreadystatechange = function(){
		if (xmlreq.readyState == 4 && xmlreq.status == 200){
	    	document.getElementById("input_nome_cad").value='';
			document.getElementById("input_nome_cad").placeholder = xmlreq.responseText;
		}
		if(document.getElementById("input_nome_cad").placeholder == "Nome já existe!"){
			document.getElementById("input_nome_cad").placeholder = "Troca o nome";
		}
	}
/*Esse acréscimo parece ser ignorado, o "else" não funciona*/	
	if(document.getElementById("input_nome_cad").placeholder != "Troca o nome"){
		document.getElementById("input_email_cad").focus();
	}else{
		document.getElementById("input_nome_cad").focus();
	}
	xmlreq.send(null);
	
}

valida_name ();

function valida_nome(){
	var filter_nome = /^([a-zA-Zà-úÀ-Ú0-9]|\s)+$/ ;
	if(!filter_nome.test(document.getElementById("input_nome_cad").value)){
	document.getElementById("input_nome_cad").value='';
	document.getElementById("input_nome_cad").placeholder = "Nome inválido";
	document.getElementById("input_nome_cad").style.borderColor = "#ff0000";
	document.getElementById("input_nome_cad").style.outline = "#ff0000";
	document.getElementById("input_nome_cad").focus();
	document.getElementById("input_nome_cad").onkeydown = function keydown_nome(){
	document.getElementById("input_nome_cad").style.borderColor = "#999999";
	document.getElementById("input_nome_cad").style.outline = null;
				}
	return false;	
	}
	return true;
}

javascript javascript-eventos

asked by anonymous 08.06.2016 / 16:51

1 answer

What should be returned in the WM_CREATE message to indicate error? What is the C ++ apvector

score 1 · Accepted Answer

Your conditions are running before the request is finished.

The only thing you need to do is move these conditions to the condition block from where the request ends (ex, if(xmlreq.readyState === 4...)... ). I even reformulated some of the code.

function nome_existe() {
    var input = document.getElementById("input_nome_cad")
    if (!/^([a-zA-Zà-úÀ-Ú0-9]|\s)+$/.test(input.value)) {
        input.value = ''
        input.placeholder = "Nome inválido"
        input.style.borderColor = "#f00"
        input.style.outline = "#f00"
        input.onkeydown = function() {
            this.style.borderColor = "#999"
            this.style.outline = null
        }
        input.focus()
        return
    }
    var request = new XMLHttpRequest
    request.open("GET"
           , "mysqli_select_ajax.php?nome_cad=" + input.value
           , true)

    request.onreadystatechange = function() {
        if (request.readyState === 4) {
            if (request.status === 200) {
                input.value = ''
                if (request.response === "Nome já existe!") {
                    input.placeholder = "Troca o nome"
                    input.focus()
                }
                else {
                    input.placeholder = request.response
                    document.getElementById("input_email_cad").focus()
                }
            }
            else {
                /* Erro de requisição. */
            }
        }
    }
    request.send()
}