https://vuejs.org/v2/guide/components.html#Form-Input-Components-using-Custom-Events
the first example about "a component to work with v-model" contain a validator function，howerver,you can not enter a number greater than 2 digits, such as 123.45, the code is as follows:

var formattedValue = value
        // Remove whitespace on either side
        .trim()
        // Shorten to 2 decimal places
        .slice(0, value.indexOf('.') + 3)

The reason is that the input will trigger an input event to trigger this validation function. When the input does not contain ".", The value.indexOf('.') always returns -1, so the .slice(0, value.indexOf('.') + 3) always returns the total .slice (0,2), thus limiting the input.
It is recommended to add a judgment as follows:

var formattedValue = value
        // Remove whitespace on either side
        .trim()
        // To determine whether it is included "." and shorten to 2 decimal places
        .slice(0, value.indexOf('.')==-1?(value.length):(value.indexOf('.')+3))