Why code not working?!

function validation() {

	var username = document.getElementById("username").value;
	var password = document.getElementById("password").value;
	var identity = document.getElementById("identity").value;
	var operation = document.getElementById("operation").value;
	var username_message = document.getElementById("username_message").value;
	var password_message = document.getElementById("password_message").value;
	var identity_message = document.getElementById("identity_message").value;
	var operation_message = document.getElementById("operation_message").value;

	if (username == null || username.length == 0) {
		document.getElementById("username_message").innerText = "❌ You forgot to fill in some important field.";
        document.getElementById("username_message").style.color = "#8a0303";
        document.getElementById("username").style.border = "1px solid #8a0303";
	} else if (username.length < 6 || username.length > 32) {
		document.getElementById("username_message").innerText = "❌ You must enter username between 6 and 32 characters.";
	    document.getElementById("username_message").style.color = "#8a0303";
	    document.getElementById("username").style.border = "1px solid #8a0303";
	} else if (username.length >= 6 && username.length < 33) {
		document.getElementById("username_message").innerText = "";
	    document.getElementById("username").style.border = "1px solid #CCC";
	} else if (password == null || password.length == 0) {
		document.getElementById("password_message").innerText = "❌ You forgot to fill in some important field.";
        document.getElementById("password_message").style.color = "#8a0303";
        document.getElementById("password").style.border = "1px solid #8a0303";
	} else if (password.length < 8 || password.length > 42) {
		document.getElementById("password_message").innerText = "❌ You must enter password between 6 and 32 characters.";
        document.getElementById("password_message").style.color = "#8a0303";
        document.getElementById("password").style.border = "1px solid #8a0303";
	} else if (password.length >= 8 || password.length < 43) {
		document.getElementById("password_message").innerText = "";
	    document.getElementById("password").style.border = "1px solid #CCC";
	} else if (identity == null || identity.length == 0) {
		document.getElementById("identity_message").innerText = "❌ You forgot to fill in some important field.";
        document.getElementById("identity_message").style.color = "#8a0303";
        document.getElementById("identity").style.border = "1px solid #8a0303";
	} else if (identity.length < 16 || identity.length > 16) {
		document.getElementById("identity_message").innerText = "❌ You must enter your real identity number.";
        document.getElementById("identity_message").style.color = "#8a0303";
        document.getElementById("identity").style.border = "1px solid #8a0303";
	} else if (identity.length == 16) {
		document.getElementById("identity_message").innerText = "";
	    document.getElementById("identity").style.border = "1px solid #CCC";
	} else if (operation == null || operation.length == 0) {
		document.getElementById("operation_message").innerText = "❌ You forgot to fill in some important field.";
        document.getElementById("operation_message").style.color = "#8a0303";
        document.getElementById("operation").style.border = "1px solid #8a0303";
	}  else {
		document.getElementById("form").action = "https://api.slapform.com/WFRPQFIf0"; 
	}
}

hi friend, how can we help you?

why code not working for login validation?

You are going to have to provide a lot more information for anyone to reasonably be able to help you.

everything working fine except else