javascript - Why does this simple regex work everywhere except html5 input pattern attribute? -

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• new regexp('^\+\d{2}\.\d{10}$') doesn't work 3 answers

this html input colours red indicate pattern has not matched when value in input "1".

var inp = document .createelement ('input'); inp .pattern = '^\d+\.?\d*$'; document .getelementbyid ("foo") .appendchild (inp); 

the regex /^\d+\.?\d*$/ matches "1" when test elsewhere. looks should too.

why form element fail match? (firefox.)

string representations, son.

your usage of pattern attribute correct in using string literals. mdn:

the regular expression language same javascript's. pattern not surrounded forward slashes.

however, in string literals have escape \ before slash gets own li'l interpretation in string literal sense. if escape it, seen actual slash , then whole pattern recognised regexp engine special character.

var inp = document.createelement('input'); inp.pattern = '^\\d+\\.?\\d*$'; document.getelementbyid("foo").appendchild(inp); 

https://jsfiddle.net/qatt3rwt/4/