Javascript模式匹配和表达式评估逻辑

Question

I have a javascript string which i want to evaluate as an expression and compare with values.

var stringExpression=">.5*{PropertyValue} + .2*{DesignValue}+ 2000 +{price}"; 

The values inside curly braces are of element id present in dom and the expression above is dynamic but the elements whose values i want to pick will always be present inside curly braces. I plan to pick these values using jquery. $("#PropertyValue").val(). Can somebody tell me how to do this evaluation in javascript post setting the values from dom and any ideas how to replace values, do i need to use split function or some regex can be used to achieve it.

You can also point me to any framework in javascript that can help in this regards.

Thanks in advance.

Answer 1

var str=">.5*{PropertyValue} + .2*{DesignValue}+ 2000 +{price}"; 

var regExp = /{(.*?)}/
var values = []
var match = str.match(regExp)
while (match != null) {
    var value = document.getElementById(match[1])
    str = str.replace(match[0], value)
    values.push(value)
    match = str.match(regExp)
}

Answer 2

Here is a solution in the functional paradigm which reads quite nicely:

function value(tag)
{
    var key = tag.substr(1, tag.length - 2) //remove braces
    return document.getElementById(key)
}


function populate(template)
{
    var tagRegExp = /{.+?}/g
    var tags = template.match(tagRegExp)
    var values = tags.map(value)
    return template.split(tagRegExp).zip(values).join("")
}

var template=">.5*{PropertyValue} + .2*{DesignValue}+ 2000 +{price}"; 
console.log(populate(template))

This solution requires a zip method for array objects which can be implemented as in the following (unless it is already provided by a library).

Array.prototype.zip = function (other) {
    function zipOne(acc, x, i, a)
    {
        if (i < other.length) {
            if (i < a.length - 1) {
                return acc.concat([x, other[i]])
            } else {
                return acc.concat([x]).concat(other.slice(i))            
            }
        } else {
            return acc.concat([x])
        }
    }

    return this.reduce(zipOne, [])
}