javascript - What is theForm.onsubmit()? -



javascript - What is theForm.onsubmit()? -

can explain function me. !theform.onsubmit() , theform.onsubmit() != false mean?

//<![cdata[ var theform = document.forms['form']; if (!theform) { theform = document.form; } function __dopostback(eventtarget, eventargument) { if (!theform.onsubmit || (theform.onsubmit() != false)) { theform.__eventtarget.value = eventtarget; theform.__eventargument.value = eventargument; theform.submit(); } } //]]>

and when checked console got this;

!theform.onsubmit true theform.onsubmit null !null true

what meaning of theform.onsubmit, how can null , !null true?

and when checked theform.onsubmit() != false got:

theform.onsubmit() typeerror: object not function theform.onsubmit() != false typeerror: object not function

what difference way between theform.onsubmit , theform.onsubmit()?

theform.onsubmit event handler submit event. if null, no handler has been set. when set, should function. theform.onsubmit() calls function, other.

you getting error theform.onsubmit() because apparently, no handler has been set. need execute entire look together.

if (!theform.onsubmit || (theform.onsubmit() != false))

if there no handler, or calling handler returns false, execute code block.

javascript javascript-events

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