lib/spring.js
function Spring(fromBody, toBody, length, coeff, weight) {
    this.from = fromBody;
    this.to = toBody;
    this.length = length;
    this.coeff = coeff;

    this.weight = typeof weight === 'number' ? weight : 1;
}
function Spring(fromBody, toBody, length, coeff, weight) {
    this.from = fromBody;
    this.to = toBody;
    this.length = length;
    this.coeff = coeff;

    this.weight = typeof weight === 'number' ? weight : 1;
}
function Spring ( fromBody , toBody , length , coeff , weight ) { this . from = fromBody ; this . to = toBody ; this . length = length ; this . coeff = coeff ; this . weight = typeof weight === 'number' ? weight : 1 ; }
Represents a physical spring. Spring connects two bodies, has rest length
stiffness coefficient and optional weight
Represents a physical spring . Spring connects two bodies has rest length stiffness coefficient and optional weight