Do JavaScript functions have to be defined?

Javascript functions do not need to be defined, just use parameters directly, but the types must correspond; JavaScript does not strictly control parameter types, for example, "function myFunction(a,b){}" is also acceptable.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

No need to define, just use the parameters directly, but the types must correspond.

javascript does not have strict control over parameter types

It is different from many other languages

For example:

function ajax(url,fnSucc,fnFaile)
{
if (window.XMLHttpRequest)
{
var oAjax = new XMLHttpRequest();
}
else
{
var oAjax = new ActiveXObject("Microsoft.XMLHTTP");
}
oAjax.open('GET', url, true);
oAjax.send();
oAjax.onreadystatechange = function () {
if (oAjax.readyState == 4)
{
if (oAjax.status == 200)
{
fnSucc(oAjax.responseText);
}
else
{
if (fnFaile)
{
fnFaile(oAjax.status);
}
}
}
};
}

[Recommended learning:javascript advanced tutorial】

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